;; X-Music, inspired by Commmon Music

#|
PATTERN SEMANTICS

Patterns are objects that are generally accessed by calling 
(next pattern). Each call returns the next item in an 
infinite sequence generated by the pattern. Items are 
organized into periods. You can access all (remaining) 
items in the current period using (next pattern t).

Patterns mark the end-of-period with +eop+, a distinguished
atom. The +eop+ markers are filtered out by the next function
but returned by the :next method.

Pattern items may be patterns. This is called a nested
pattern.  When patterns are nested, you return a period 
from the innermost pattern, i.e. traversal is depth-first. 
This means when you are using something like random, you
have to remember the last thing returned and keep getting
the next element from that thing until you see +eop+; 
then you move on. It's a bit more complicated because 
a pattern advances when its immediate child pattern
finishes a cycle, but +eop+ is only returned from the
"leaf" patterns.

With nested patterns, i.e. patterns with items that
are patterns, the implementation requires that
*all* items must be patterns. The application does
*not* have to make every item a pattern, so the
implementation "cleans up" the item list: Any item
that is not a pattern is be replaced with a cycle
pattern whose list contains just the one item.

EXPLICIT PATTERN LENGTH

Pattern length may be given explicitly by a number or
a pattern that generates numbers. Generally this is 
specified as the optional :for keyword parameter when
the pattern is created. If the explicit pattern
length is a number, this will be the period length,
overriding all implicit lengths. If the pattern length
is itself a pattern, the pattern is evaluated every 
period to determine the length of the next period,
overriding any implicit length. 

IMPLEMENTATION

There are 3 ways to determine lengths: 
1) The length is implicit. The length can be
computed (at some point) and turned into an
explicit length.

2) The length is explicit. This overrides the
implicit length. The explicit length is stored as
a counter that tells how many more items to generate
in the current period.

3) The length can be generated by a pattern.
The pattern is evaluated to generate an explicit
length.

So ultimately, we just need a mechanism to handle
explicit lengths. This is incorporated into the
pattern-class. The pattern-class sends :start-period
before calling :advance when the first item in a
period is about to be generated. Also, :next returns
+eop+ automatically at the end of a period.

Because evaluation is "depth first," i.e. we 
advance to the next top-level item only after a period
is generated from a lower-level pattern, every pattern
has a "current" field that holds the current item. the
"have-current" field is a flag to tell when the "current"
field is valid. It is initialized to nil.

To generate an element, you need to follow the nested
patterns all the way to the leaf pattern for every 
generated item. This is perhaps less efficient than
storing the current leaf pattern at the top level, but
patterns can be shared, i.e. a pattern can be a 
sub-pattern of multiple patterns, so current position
in the tree structure of patterns can change at 
any time.

The evaluation of nested patterns is depth-first
and the next shallower level advances when its current
child pattern completes a cycle. To facilitate this
step, the :advance method, which advances a pattern
and computes "current", returns +eonp+, which is a
marker that a nested pattern has completed a cycle.

The :next method generates the next item or +eop+ from
a pattern. The algorithm in psuedo-code is roughly this:

next(p)
    while true:
        if not have-current
            pattern-advance()
            have-current = true
            if is-nested and current = eop:
                have-current = false
                return eonp
        if is-nested:
            rslt = next(current)
            if rslt == eonp
                have-current = false
            elif rslt == eop and not current.is-nested
                have-current = false
                return rslt
            else
                return rslt
        else
            have-current = nil
            return current

pattern-advance
    // length-pattern is either a pattern or a constant
    if null(count) and length-pattern:
        count = next(length-pattern)
        start-period() // subclass-specific computation
    if null(count)
        error
    if count == 0
        current = eop
        count = nil
    else
        advance() // subclass-specific computation
        count--


SUBCLASS RESPONSIBILITIES

Note that :advance is the method to override in the 
various subclasses of pattern-class. The :advance()
method computes the next element in the infinite
sequence of items and puts the item in the "current"
field. 

The :start-period method is called before calling 
advance to get the first item of a new period.

Finally, set the is-nested flag if there are nested patterns,
and make all items of any nested pattern be patterns (no
mix of patterns and non-patterns is allowed; use 
    (MAKE-CYCLE (LIST item))
to convert a non-pattern to a pattern).

|#

(setf SCORE-EPSILON 0.000001)

(setf pattern-class 
  (send class :new '(current have-current is-nested name count
                     length-pattern trace)))

(defun patternp (x) 
  (and (objectp x) (send x :isa pattern-class)))

(setf +eop+ '+eop+)
(setf +eonp+ '+eonp+) ;; end of nested period, this indicates you
   ;; should advance yourself and call back to get the next element

(defun check-for-list (lis name)
  (if (not (listp lis))
      (error (format nil "~A, requires a list of elements" name))))

(defun check-for-list-or-pattern (lis name)
  (if (not (or (listp lis) (patternp lis)))
      (error (format nil "~A, requires a list of elements or a pattern" name))))

(defun list-has-pattern (lis)
  (dolist (e lis) 
    (if (patternp e) (return t))))

(defun is-homogeneous (lis)
  (let (type)
    (dolist (elem lis t)
      (cond ((null type)
             (setf type (if (patternp elem) 'pattern 'atom)))
            ((and (eq type 'pattern)
                  (not (patternp elem)))
             (return nil))
            ((and (eq type 'atom)
                  (patternp elem))
             (return nil))))))

(defun make-homogeneous (lis)
  (cond ((is-homogeneous lis) lis)
        (t
         (mapcar #'(lambda (item)
                     (if (patternp item) item 
                         (make-cycle (list item)
                          ;; help debugging by naming the new pattern
                          ;; probably, the name could be item, but
                          ;; here we coerce item to a string to avoid
                          ;; surprises in code that assumes string names.
                          :name (format nil "~A" item))))
                 lis))))


(send pattern-class :answer :next '()
  '(;(display ":next" name is-nested)
    (loop
     (cond ((not have-current)
            (send self :pattern-advance)
            (setf have-current t)
            (cond (trace
                   (format t "pattern ~A advanced to ~A~%"
                           (if name name "<no-name>")
                           (if (patternp current) 
                               (if (send current :name)
                                   (send current :name)
                                   "<a-pattern>")
                               current))))
            (cond ((and is-nested (eq current +eop+))
                   ;(display ":next returning eonp" name)
                   (setf have-current nil)
                   (return +eonp+)))))
     (cond (is-nested
            (let ((rslt (send current :next)))
              (cond ((eq rslt +eonp+)
                     (setf have-current nil))
                    ;; advance next-to-leaf level at end of leaf's period
                    ((and (eq rslt +eop+) (not (send current :is-nested)))
                     (setf have-current nil)
                     ;; return +eof+ because it's the end of leaf's period
                     (return rslt))
                    (t
                     (return rslt)))))
           (t
            (setf have-current nil)
            (return current))))))


;; :PATTERN-ADVANCE -- advance to the next item in a pattern
;; 
;; this code is used by every class. class-specific behavior
;; is implemented by :advance, which this method calls
;;
(send pattern-class :answer :pattern-advance '()
  '(;(display "enter :pattern-advance" self name count current is-nested)
    (cond ((null count)
           ;(display "in :pattern-advance" name count length-pattern)
           (if length-pattern
               (setf count (next length-pattern)))
           ;; if count is still null, :start-period must set count
           (send self :start-period)))
    (cond ((null count)
           (error
            (format nil
             "~A, pattern-class :pattern-advance has null count" name))))
    (cond ((zerop count)
           (setf current +eop+)
           (setf count nil))
          (t
           (send self :advance)
           (decf count)))
    ;(display "exit :pattern-advance" name count current)
    ))


(send pattern-class :answer :is-nested '() '(is-nested))


(send pattern-class :answer :name '() '(name))


(send pattern-class :answer :set-current '(c)
  '((setf current c)
    (let ((value
           (if (patternp current) 
               (send current :name)
               current)))
      ;(display ":set-current" name value)
      )))


;; next -- get the next element in a pattern
;;
;; any non-pattern value is simply returned
;;
(defun next (pattern &optional period-flag) 
  ;(display "next" pattern period-flag (patternp pattern))
  (cond ((and period-flag (patternp pattern))
         (let (rslt elem)
           (while (not (eq (setf elem (send pattern :next)) +eop+))
               ;(display "next t" (send pattern :name) elem)
               (if (not (eq elem +eonp+)) 
                   (push elem rslt)))
           (reverse rslt)))
        (period-flag
         (display "next" pattern)
         (error (format nil "~A, next expected a pattern"
                            (send pattern :name))))
        ((patternp pattern)
         ;(display "next" (send pattern :name) pattern)
         (let (rslt)
           (dotimes (i 10000 (error
                 (format nil
                  "~A, just retrieved 10000 empty periods -- is there a bug?"
                  (send pattern :name))))
             (if (not (member (setf rslt (send pattern :next)) 
                              '(+eop+ +eonp+)))
                 (return rslt)))))
        (t ;; pattern not a pattern, so just return it:
         ;(display "next" pattern)
         pattern)))

;; ---- LENGTH Class ----

(setf length-class 
  (send class :new '(pattern length-pattern) '() pattern-class))

(send length-class :answer :isnew '(p l nm tr)
  '((setf pattern p length-pattern l name nm trace tr)))

;; note that count is used as a flag as well as a counter.
;; If count is nil, then the pattern-length has not been
;; determined. Count is nil intitially and again at the 
;; end of each period. Otherwise, count is an integer
;; used to count down the number of items remaining in 
;; the period.

(send length-class :answer :start-period '()
  '((setf count (next length-pattern))))

(send length-class :answer :advance '()
  '((send self :set-current (next pattern))))

(defun make-length (pattern length-pattern &key (name "length") trace)
  (send length-class :new pattern length-pattern name trace))

;; ---- CYCLE Class ---------

(setf cycle-class (send class :new 
                        '(lis cursor lis-pattern)
                        '() pattern-class))

(send cycle-class :answer :isnew '(l for nm tr)
  '((cond ((patternp l)
           (setf lis-pattern l))
          ((listp l)
           (send self :set-list l))
          (t
           (error (format nil "~A, expected list" nm) l)))
    (setf length-pattern for name nm trace tr)))


(send cycle-class :answer :set-list '(l)
  '((setf lis l)
    (check-for-list lis "cycle-class :set-list")
    (setf is-nested (list-has-pattern lis))
    (setf lis (make-homogeneous lis))))


(send cycle-class :answer :start-period '()
  '(;(display "cycle-class :start-period" lis-pattern lis count length-pattern)
    (cond (lis-pattern
           (send self :set-list (next lis-pattern t))
           (setf cursor lis)))
    (if (null count)
        (setf count (length lis)))))
  

(send cycle-class :answer :advance '()
  '((cond ((and (null cursor) lis)
           (setf cursor lis))
          ((null cursor)
           (error (format nil "~A, :advance - no items" name))))
    (send self :set-current (car cursor))
    (pop cursor)))


(defun make-cycle (lis &key for (name "cycle") trace)
   (check-for-list-or-pattern lis "make-cycle")
   (send cycle-class :new lis for name trace))

;; ---- LINE class ----

(setf line-class (send class :new '(lis cursor lis-pattern) 
                       '() pattern-class))

(send line-class :answer :isnew '(l for nm tr)
  '((cond ((patternp l)
           (setf lis-pattern l))
          ((listp l)
           (send self :set-list l))
          (t
           (error (format nil "~A, expected list" nm) l)))
    (setf length-pattern for name nm trace tr)))

(send line-class :answer :set-list '(l)
  '((setf lis l)
    (check-for-list lis "line-class :set-list")
    (setf is-nested (list-has-pattern lis))
    (setf lis (make-homogeneous l))
    (setf cursor lis)))


(send line-class :answer :start-period '()
  '((cond (lis-pattern
           (send self :set-list (next lis-pattern t))
           (setf cursor lis)))
    (if (null count)
        (setf count (length lis)))))


(send line-class :answer :advance '()
  '((cond ((null cursor)
           (error (format nil "~A, :advance - no items" name))))
    (send self :set-current (car cursor))
    (if (cdr cursor) (pop cursor))))
  

(defun make-line (lis &key for (name "line") trace)
   (check-for-list-or-pattern lis "make-line")
   (send line-class :new lis for name trace))


;; ---- RANDOM class -----

(setf random-class (send class :new 
       '(lis lis-pattern len previous repeats mincnt maxcnt) 
       '() pattern-class))

;; the structure is (value weight weight-pattern max min)
(setfn rand-item-value car)
(defun set-rand-item-value (item value) (setf (car item) value))
(setfn rand-item-weight cadr)
(defun set-rand-item-weight (item weight) (setf (car (cdr item)) weight))
(setfn rand-item-weight-pattern caddr)
(setfn rand-item-max cadddr)
(defun rand-item-min (lis) (car (cddddr lis)))


(defun select-random (len lis previous repeats mincnt maxcnt)
  (let (sum items r)
    (cond ((zerop len)
           (break "random-class has no list to choose from")
           nil)
          (t
           (setf sum 0)
           (dolist (item lis)
             (setf sum (+ sum (rand-item-weight item))))
           (setf items lis)
           (setf r (rrandom))
           (setf sum (* sum r))
           (setf rbd-count-all (incf rbd-count-all))
           (loop
             (setf sum (- sum (rand-item-weight (car items))))
             (if (<= sum 0) (return (car items)))
             (setf rbd-count-two (incf rbd-count-two))
             (setf items (cdr items)))))))


(defun random-convert-spec (item)
  ;; convert (value :weight wp :min min :max max) to (value nil wp max min)
  (let (value (wp 1) mincnt maxcnt lis)
    (setf value (car item))
    (setf lis (cdr item))
    (while lis
      (cond ((eq (car lis) :weight)
             (setf wp (cadr lis)))
            ((eq (car lis) :min)
             (setf mincnt (cadr lis)))
            ((eq (car lis) :max)
             (setf maxcnt (cadr lis)))
            (t
             (error "(make-random) item syntax error" item)))
      (setf lis (cddr lis)))
    (list value nil wp maxcnt mincnt)))


(defun random-atom-to-list (a)
  (if (atom a)
      (list a nil 1 nil nil)
      (random-convert-spec a)))


(send random-class :answer :isnew '(l for nm tr)
  ;; there are two things we have to normalize:
  ;; (1) make all items lists
  ;; (2) if any item is a pattern, make all items patterns
  '((cond ((patternp l)
           (setf lis-pattern l))
          ((listp l)
           (send self :set-list l))
          (t
           (error (format nil "~A, expected list") l)))
    (setf rbd-count-all 0 rbd-count-two 0)
    (setf length-pattern for name nm trace tr)))


(send random-class :answer :set-list '(l)
  '((check-for-list l "random-class :set-list")
    (setf lis (mapcar #'random-atom-to-list l))
    (dolist (item lis)
      (if (patternp (rand-item-value item))
          (setf is-nested t)))
    (if is-nested
        (mapcar #'(lambda (item)
                    (if (not (patternp (rand-item-value item)))
                        (set-rand-item-value item 
                         (make-cycle (list (rand-item-value item))))))
                lis))
    ;(display "random is-new" lis)
    (setf repeats 0)
    (setf len (length lis))))

    
(send random-class :answer :start-period '()
  '(;(display "random-class :start-period" count len lis lis-pattern)
    (cond (lis-pattern
           (send self :set-list (next lis-pattern t))))
    (if (null count)
        (setf count len))
    (dolist (item lis)
      (set-rand-item-weight item (next (rand-item-weight-pattern item))))))


(send random-class :answer :advance '()
  '((let (selection (iterations 0))
      ;(display "random-class :advance" mincnt repeats)
      (cond ((and mincnt (< repeats mincnt))
             (setf selection previous)
             (incf repeats))
            (t
             (setf selection
                   (select-random len lis previous repeats mincnt maxcnt))))
      (loop ; make sure selection is ok, otherwise try again
        (cond ((and (eq selection previous)
                    maxcnt 
                    (>= repeats maxcnt)) ; hit maximum limit, try again
               (setf selection
                     (select-random len lis previous repeats mincnt maxcnt))
               (incf iterations)
               (cond ((> iterations 10000)
                      (error
                        (format nil
                         "~A, unable to pick next item after 10000 tries"
                         name)
                       lis))))
              (t (return)))) ; break from loop, we found a selection

        ; otherwise, we are ok
        (if (not (eq selection previous))
            (setf repeats 1)
            (incf repeats))
        (setf mincnt (rand-item-min selection))
        (setf maxcnt (rand-item-max selection))
        (setf previous selection)
        ;(display "new selection" repeats mincnt maxcnt selection)
        (send self :set-current (rand-item-value selection)))))
      

(defun make-random (lis &key for (name "random") trace)
   (check-for-list-or-pattern lis "make-random")
   (send random-class :new lis for name trace))


;; ---- PALINDROME class -----

#| Palindrome includes elide, which is either t, nil, :first, or :last.
The pattern length is the "natural" length of the pattern, which goes
forward and backward through the list. Thus, if the list is of length N,
the palindrome length depends on elide as follows:
    elide   length
     nil      2N
     t        2N - 2
   :first     2N - 1
   :last      2N - 1
If elide is a pattern, and if length is not specified, then length should
be computed based on elide. 
|#


(setf palindrome-class (send class :new 
                         '(lis revlis lis-pattern 
                           direction elide-pattern
                           elide cursor)
                         '() pattern-class))

(send palindrome-class :answer :set-list '(l)
  '((setf lis l)
    (check-for-list lis "palindrome-class :start-period")
    (setf is-nested (list-has-pattern lis))
    (setf lis (make-homogeneous l))
    (setf revlis (reverse lis)
          direction t
          cursor lis)))


(send palindrome-class :answer :isnew '(l e for nm tr)
  '((cond ((patternp l)
           (setf lis-pattern l))
          ((listp l)
           (send self :set-list l))
          (t
           (error (format nil "~A, expected list" nm) l)))
    (setf elide-pattern e length-pattern for name nm trace tr)))


(send palindrome-class :answer :start-period '()
  '((cond (lis-pattern
           (send self :set-list (next lis-pattern t))
           (setf cursor lis)))
    (setf elide (next elide-pattern))
    (if (and elide (null lis))
        (error (format nil "~A, cannot elide if list is empty" name)))
    (if (null count)
        (setf count (- (* 2 (length lis))
                       (if (member elide '(:first :last)) 
                           1
                           (if elide 2 0)))))))


(send palindrome-class :answer :next-item '()
  '((send self :set-current (car cursor))
    (pop cursor)
    (cond ((and cursor (not (cdr cursor))
                (or (and direction (member elide '(:last t)))
                    (and (not direction) (member elide '(:first t)))))
           (pop cursor)))))


(send palindrome-class :answer :advance '()
  '(
    (cond (cursor
           (send self :next-item))
          (direction ;; we're going forward
           (setf direction nil) ;; now going backward
           (setf cursor revlis)
           (send self :next-item))
          (t ;; direction is reverse
           (setf direction t)
           (setf cursor lis)
           (send self :next-item)))))


(defun make-palindrome (lis &key elide for (name "palindrome") trace)
  (check-for-list-or-pattern lis "make-palindrome")
  (send palindrome-class :new lis elide for name trace))


;; ================= HEAP CLASS ======================

;; to handle the :max keyword, which tells the object to avoid
;; repeating the last element of the previous period:
;;
;; maxcnt = 1 means "avoid the repetition"
;; check-repeat signals we are at the beginning of the period and must check
;; prev holds the previous value (initially nil)
;; after each item is generated, check-repeat is cleared. It is
;; recalculated when a new period is started.

(setf heap-class (send class :new '(lis used maxcnt prev check-repeat
                                    lis-pattern len)
                       '() pattern-class))

(send heap-class :answer :isnew '(l for mx nm tr)
  '((cond ((patternp l)
           (setf lis-pattern l))
          ((listp l)
           ; make a copy of l to avoid side effects
           (send self :set-list (append l nil)))
          (t
           (error (format nil "~A, expected list" nm) l)))
    (setf length-pattern for maxcnt mx name nm trace tr)))


(send heap-class :answer :set-list '(l)
  '((setf lis l)
    (check-for-list lis "heap-class :set-list")
    (setf is-nested (list-has-pattern lis))
    (setf lis (make-homogeneous lis))
    (setf len (length lis))))


(send heap-class :answer :start-period '()
  '(;(display "heap-class :start-period" lis-pattern count lis)
    (cond (lis-pattern
           (send self :set-list (next lis-pattern t))))
    ; start of period -- may need to avoid repeating previous item
    (if (= maxcnt 1) (setf check-repeat t))
    (if (null count)
        (setf count len))))

    
(defun delete-first (elem lis)
  (cond ((null lis) nil)
        ((eq elem (car lis))
         (cdr lis))
        (t
         (cons (car lis) (delete-first elem (cdr lis))))))


;; NO-DISTINCT-ELEM -- check if any element of list is not val
;;
(defun no-distinct-elem (lis val)
  (not 
    (dolist (elem lis)
      (if (not (equal elem val))
          ;; there is a distinct element, return t from dolist
          (return t)))))
    ;; if no distinct element, dolist returns nil, but this is negated
    ;; by the NOT so the function will return t


(send heap-class :answer :advance '()
  '((cond ((null lis)
           (setf lis used)
           (setf used nil)))
    (let (n elem)
      (cond ((and check-repeat (no-distinct-elem lis prev))
             (error (format nil "~A, cannot avoid repetition, but :max is 1"
                                name))))
      (loop 
        (setf n (random (length lis)))
        (setf elem (nth n lis))
        (if (or (not check-repeat) (not (equal prev elem))) 
            (return))) ;; loop until suitable element is chosen
      (setf lis (delete-first elem lis))
      (push elem used)
      (setf check-repeat nil)
      (setf prev elem)
      (send self :set-current elem))))

(defun make-heap (lis &key for (max 2) (name "heap") trace)
  (send heap-class :new lis for max name trace))

;;================== COPIER CLASS ====================

(setf copier-class (send class :new '(sub-pattern repeat repeat-pattern 
                                      merge merge-pattern period cursor) 
                                    '() pattern-class))

(send copier-class :answer :isnew '(p r m for nm tr)
  '((setf sub-pattern p repeat-pattern r merge-pattern m)
    (setf length-pattern for name nm trace tr)))


#| copier-class makes copies of periods from sub-pattern

If merge is true, the copies are merged into one big period.
If merge is false, then repeat separate periods are returned.
If repeat is negative, then -repeat periods of sub-pattern
are skipped.

merge and repeat are computed from merge-pattern and 
repeat-pattern initially and after making repeat copies

To repeat individual items, set the :for keyword parameter of
the sub-pattern to 1.
|#

(send copier-class :answer :start-period '()
  '((cond ((null count) 
           (cond ((or (null repeat) (zerop repeat))
                  (send self :really-start-period))
                 (t
                  (setf count (length period))))))))


(send copier-class :answer :really-start-period '()
  '(;(display "copier-class :really-start-period" count)
    (setf merge (next merge-pattern))
    (setf repeat (next repeat-pattern))
    (while (minusp repeat)
      (dotimes (i (- repeat))
        (setf period (next sub-pattern t)))
      (setf repeat (next repeat-pattern))
      (setf merge (next merge-pattern)))
    (setf period (next sub-pattern t))
    (setf cursor nil)
    (if (null count)
        (setf count (* (if merge repeat 1)
                       (length period))))))


(send copier-class :answer :advance '()
  '((let ((loop-count 0))
      (loop
        ;(display "copier loop" repeat cursor period)
        (cond (cursor
               (send self :set-current (car cursor))
               (pop cursor)
               (return))
              ((plusp repeat)
               (decf repeat)
               (setf cursor period))
              ((> loop-count 10000)
               (error (format nil
                "~A, copier-class :advance encountered 10000 empty periods"
                name)))
              (t
               (send self :really-start-period)))
        (incf loop-count)))))


(defun make-copier (sub-pattern &key for (repeat 1) merge (name "copier") trace)
  (send copier-class :new sub-pattern repeat merge for name trace))
   
;; ================= ACCUMULATE-CLASS ===================

(setf accumulate-class (send class :new '(sub-pattern period cursor sum mini maxi) 
                                    '() pattern-class))


(send accumulate-class :answer :isnew '(p for nm tr mn mx)
  '((setf sub-pattern p length-pattern for name nm trace tr sum 0 mini mn maxi mx)
    ; (display "accumulate isnew" self nm)
    ))


#| 
accumulate-class creates sums of numbers from another pattern
The output periods are the same as the input periods (by default).
|#

(send accumulate-class :answer :start-period '()
  '((cond ((null count)
           (send self :really-start-period)))))


(send accumulate-class :answer :really-start-period '()
  '((setf period (next sub-pattern t))
    (setf cursor period)
    ;(display "accumulate-class :really-start-period" period cursor count)
    (if (null count)
        (setf count (length period)))))


(send accumulate-class :answer :advance '()
  '((let ((loop-count 0) (minimum (next mini)) (maximum (next maxi)))
      (loop
        (cond (cursor
               (setf sum (+ sum (car cursor)))
               (cond ((and (numberp minimum) (< sum minimum))
                      (setf sum minimum)))
               (cond ((and (numberp maximum) (> sum maximum))
                      (setf sum maximum)))
               (send self :set-current sum)
               (pop cursor)
               (return))
              ((> loop-count 10000)
               (error (format nil
                "~A, :advance encountered 10000 empty periods" name)))
              (t
               (send self :really-start-period)))
        (incf loop-count)))))


(defun make-accumulate (sub-pattern &key for min max (name "accumulate") trace)
  (send accumulate-class :new sub-pattern for name trace min max))
   
;;================== ACCUMULATION CLASS ===================

;; for each item, generate all items up to and including the item, e.g.
;; (a b c) -> (a a b a b c)

(setf accumulation-class (send class :new '(lis lis-pattern outer inner len)
                               '() pattern-class))

(send accumulation-class :answer :isnew '(l for nm tr)
  '((cond ((patternp l)
           (setf lis-pattern l))
          ((listp l)
           (send self :set-list l))
          (t
           (error (format nil "~A, expected list" nm) l)))
      (setf length-pattern for name nm trace tr)))

(send accumulation-class :answer :set-list '(l)
  '((setf lis l)
    (check-for-list lis "heap-class :set-list")
    (setf lis (make-homogeneous lis))
    (setf inner lis)
    (setf outer lis)
    (setf len (length lis))))

(send accumulation-class :answer :start-period '()
  '((cond (lis-pattern
           (send self :set-list (next lis-pattern t))))
    ; start of period, length = (n^2 + n) / 2
    (if (null count) (setf count (/ (+ (* len len) len) 2)))))

(send accumulation-class :answer :advance '()
  ;; inner traverses lis from first to outer
  ;; outer traverses lis
  '((let ((elem (car inner)))
      (cond ((eq inner outer)
             (setf outer (rest outer))
             (setf outer (if outer outer lis))
             (setf inner lis))
            (t
             (setf inner (rest inner))))
      (send self :set-current elem))))

(defun make-accumulation (lis &key for (name "accumulation") trace)
  (send accumulation-class :new lis for name trace))


;;================== SUM CLASS =================

(setf sum-class (send class :new '(x y period cursor fn) '() pattern-class))

(send sum-class :answer :isnew '(xx yy for nm tr)
  '((setf x xx y yy length-pattern for name nm trace tr fn #'+)))

#|
sum-class creates pair-wise sums of numbers from 2 streams.
The output periods are the same as the input periods of the first
pattern argument (by default).
|#

(send sum-class :answer :start-period '()
  '((cond ((null count)
           (send self :really-start-period)))))

(send sum-class :answer :really-start-period '()
  '((setf period (next x t))
    (setf cursor period)
    (if (null count)
        (setf count (length period)))))

(send sum-class :answer :advance '()
  '((let ((loop-count 0) rslt)
      (loop
        (cond (cursor
               (setf rslt (funcall fn (car cursor) (next y)))
               (send self :set-current rslt)
               (pop cursor)
               (return))
              ((> loop-count 10000)
               (error (format nil
                       "~A, :advance encountered 10000 empty periods" name)))
              (t
               (send self :really-start-period)))
        (incf loop-count)))))


(defun make-sum (x y &key for (name "sum") trace)
  (send sum-class :new x y for name trace))               


;;================== PRODUCT CLASS =================

(setf product-class (send class :new '() '() sum-class))

(send product-class :answer :isnew '(xx yy for nm tr)
  '((setf x xx y yy length-pattern for name nm trace tr fn #'*)))

(defun make-product (x y &key for (name "product") trace)
  (send product-class :new x y for name trace))               


;;================== EVAL CLASS =================

(setf eval-class (send class :new '(expr expr-pattern) 
                       '() pattern-class))

(send eval-class :answer :isnew '(e for nm tr)
  '((cond ((patternp e)
           (setf expr-pattern e))
          (t
           (setf expr e)))
    (setf length-pattern for name nm trace tr)))


(send eval-class :answer :start-period '()
  '(;(display "cycle-class :start-period" lis-pattern lis count length-pattern)
    (cond (expr-pattern
           (setf expr (next expr-pattern))))))
  

(send eval-class :answer :advance '()
  '((send self :set-current (eval expr))))


(defun make-eval (expr &key (for 1) (name "eval") trace)
   (send eval-class :new expr for name trace))

;;================== MARKOV CLASS ====================

(setf markov-class (send class :new 
      '(rules order state produces pattern len) 
      '() pattern-class))


(defun is-produces-homogeneous (produces)
  (let (type elem)
    (setf *rslt* nil)
    (loop
      (cond ((or (null produces) (eq produces :eval) (null (cadr produces)))
             (return t)))
      (setf elem (cadr produces))
      (cond ((null type)
             (setf type (if (patternp elem) 'pattern 'atom))
           ;(display "is-produces-homogeneous" type)
             (setf *rslt* (eq type 'pattern))
             ;(display "is-produces-homogeneous" *rslt*)
             )
            ((and (eq type 'pattern) (not (patternp elem)))
             (return nil))
            ((and (eq type 'atom)
                  (patternp elem))
             (return nil)))
      (setf produces (cddr produces)))))


(defun make-produces-homogeneous (produces)
  (let (result item)
    (loop
      (if (null produces) (return nil))
      (push (car produces) result)
      (setf produces (cdr produces))
      (setf item (car produces))
      (setf produces (cdr produces))
      (if (not (patternp item)) 
        (setf item (make-cycle (list item))))
      (push item result))
    (reverse result)))


(send markov-class :answer :isnew '(r o s p for nm tr)
  ;; input parameters are rules, order, state, produces, for, name, trace
  '((setf order o state s produces p length-pattern for name nm trace tr)
    (setf len (length r))
    ;; input r looks like this:
    ;; ((prev1 prev2 -> next1 next2 (next3 weight) ... ) ...)
    ;; transition table will look like a list of these:
    ;; ((prev1 prev2 ... prevn) (next1 weight weight-pattern) ...)
    (dolist (rule r)
      (let ((targets (cdr (nthcdr order rule)))
            entry pattern)
        ;; build entry in reverse order
        (dolist (target targets)
          (push (if (atom target)
                    (list target 1 1) 
                    (list (first target) 
                          (next (second target)) 
                          (second target))) 
                entry))
        ; (display "isnew" entry rule targets order (nthcdr order rule))
        (dotimes (i order)
          (push (nth i rule) pattern))
        (push (cons (reverse pattern) entry) rules)))
    (setf rules (reverse rules)) ;; keep rules in original order
    (setf *rslt* nil) ;; in case produces is nil
    (cond ((and produces (not (is-produces-homogeneous produces)))
           (setf produces (make-produces-homogeneous produces))))
    ;(display "markov-class :isnew" *rslt*)
    (setf is-nested *rslt*) ;; returned by is-produces-homogeneous
    ;(display "markov-class :isnew" is-nested)
    ))


(defun markov-match (state pattern)
  (dolist (p pattern t) ;; return true if no mismatch
    ;; compare element-by-element
    (cond ((eq p '*)) ; anything matches '*
          ((eql p (car state)))
          (t (return nil))) ; a mismatch: return false
    (setf state (cdr state))))

(defun markov-sum-of-weights (rule)
  ;(display "sum-of-weights" rule)
  (let ((sum 0.0))
    (dolist (target (cdr rule))
      ;(display "markov-sum-of-weights" target)
      (setf sum (+ sum (second target))))
    sum))


(defun markov-pick-target (sum rule)
  (let ((total 0.0)
        ;; want to choose a value in the interval [0, sum)
        ;; but real-random is not open on the right, so fudge
        ;; the range by a small amount:
        (r (real-random 0.0 (- sum SCORE-EPSILON))))
    (dolist (target (cdr rule))
      (setf total (+ total (second target)))
      (cond ((> total r) (return (car target)))))))


(defun markov-update-weights (rule)
  (dolist (target (cdr rule))
    (setf (car (cdr target)) (next (caddr target)))))


(defun markov-map-target (target produces)
  (while (and produces (not (eq target (car produces))))
    (setf produces (cddr produces)))
  (cadr produces))


(send markov-class :answer :find-rule '()
  '((let (rslt)
      ;(display "find-rule" rules)
      (dolist (rule rules)
        ;(display "find-rule" state rule)
        (cond ((markov-match state (car rule))
               (setf rslt rule)
               (return rslt))))
      (cond ((null rslt)
             (display "Error, no matching rule found" state rules)
             (error (format nil "~A, (markov-class)" name))))
      rslt)))


(send markov-class :answer :start-period '()
  '((if (null count)
        (setf count len))))

(defun markov-general-rule-p (rule)
  (let ((pre (car rule)))
    (cond ((< (length pre) 2) nil) ;; 1st-order mm
          (t
           ;; return false if any member not *
           ;; return t if all members are *
           (dolist (s pre t)
             (if (eq s '*) t (return nil)))))))

(defun markov-find-state-leading-to (target rules)
  (let (candidates)
    (dolist (rule rules)
      (let ((targets (cdr rule)))
        (dolist (targ targets)
          (cond ((eql (car targ) target)
                 (push (car rule) candidates))))))
    (cond (candidates ;; found at least one
           (nth (random (length candidates)) candidates))
          (t
           nil))))

(send markov-class :answer :advance '()
  '((let (rule sum target rslt new-state)
      ;(display "markov" pattern rules)
      (setf rule (send self :find-rule))
      ;(display "advance 1" rule)
      (markov-update-weights rule)
      ;(display "advance 2" rule)
      (setf sum (markov-sum-of-weights rule))
      ;; the target can be a pattern, so apply NEXT to it
      (setf target (next (markov-pick-target sum rule)))
      ;; if the matching rule is multiple *'s, then this
      ;; is a higher-order Markov model, and we may now
      ;; wander around in parts of the state space that
      ;; never appeared in the training data. To avoid this
      ;; we violate the strict interpretation of the rules
      ;; and pick a random state sequence from the rule set
      ;; that might have let to the current state. We jam
      ;; this state sequence into state so that when we
      ;; append target, we'll have a history that might
      ;; have a corresponding rule next time.
      (cond ((markov-general-rule-p rule)
             (setf new-state (markov-find-state-leading-to target rules))
             (cond (new-state
                    ;(display "state replacement" new-state target)
                    (setf state new-state)))))
      (setf state (append (cdr state) (list target)))
      ;(display "markov next" rule sum target state)
      ;; target is the symbol for the current state. We can
      ;; return target (default), the value of target, or a
      ;; mapped value:
      (cond ((eq produces :eval)
             (setf target (eval target)))
            ((and produces (listp produces))
             ;(display "markov-produce" target produces)
             (setf target (markov-map-target target produces))))
      (if (not (eq is-nested (patternp target)))
          (error (format nil 
         "~A :is-nested keyword (~A) not consistent with result (~A)"
                  name is-nested target)))
      (send self :set-current target))))


(defun make-markov (rules &key produces past for (name "markov") trace)
  ;; check to make sure past and rules are consistent
  (let ((order (length past)))
    (dolist (rule rules)
      (dotimes (i order)
        (if (eq (car rule) '->)
            (error (format nil "~A, a rule does not match the length of :past"
                               name)))
        (pop rule))
      (if (eq (car rule) '->) nil
          (error (format nil "~A, a rule does not match the length of :past"
                             name)))))
  (cond ((null for)
         (setf for (length rules))))
  (send markov-class :new rules (length past) past produces for name trace))


(defun markov-rule-match (rule state)
  (cond ((null state) t)
        ((eql (car rule) (car state))
         (markov-rule-match (cdr rule) (cdr state)))
        (t nil)))


(defun markov-find-rule (rules state)
  (dolist (rule rules)
    ;(display "find-rule" rule)
    (cond ((markov-rule-match rule state)
           (return rule)))))

;; ------- functions below are for MARKOV-CREATE-RULES --------

;; MARKOV-FIND-CHOICE -- given a next state, find it in rule
;;
;; use state to get the order of the Markov model, e.g. how
;; many previous states to skip in the rule, (add 1 for '->).
;; then use assoc to do a quick search
;;
;; example:
;;  (markov-find-choice '(a b -> (c 1) (d 2)) '(a b) 'd)
;; returns (d 2) from the rule
;;
(defun markov-find-choice (rule state next)
  (assoc next (nthcdr (1+ (length state)) rule)))

(defun markov-update-rule (rule state next)
  (let ((choice (markov-find-choice rule state next)))
    (cond (choice
           (setf (car (cdr choice)) (1+ (cadr choice))))
          (t
           (nconc rule (list (list next 1)))))
    rule))


(defun markov-update-rules (rules state next)
  (let ((rule (markov-find-rule rules state)))
    (cond (rule
           (markov-update-rule rule state next))
          (t
           (setf rules
                 (nconc rules 
                        (list (append state
                                      (cons '-> (list 
                                                 (list next 1)))))))))
    rules))


;; MARKOV-UPDATE-HISTOGRAM -- keep a list of symbols and counts
;; 
;; This histogram will become the right-hand part of a rule, so
;; the format is ((symbol count) (symbol count) ...)
;;
(defun markov-update-histogram (histogram next)
  (let ((pair (assoc next histogram)))
    (cond (pair
           (setf (car (cdr pair)) (1+ (cadr pair))))
          (t
           (setf histogram (cons (list next 1) histogram))))
    histogram))


(defun markov-create-rules (sequence order &optional generalize)
  (let ((seqlen (length sequence)) state rules next histogram rule)
    (cond ((<= seqlen order)
           (error "markov-create-rules: sequence must be longer than order"))
          ((< order 1)
           (error "markov-create-rules: order must be 1 or greater")))
    ; build initial state sequence
    (dotimes (i order)
      (setf state (nconc state (list (car sequence))))
      (setf sequence (cdr sequence)))
    ; for each symbol, either update a rule or add a rule
    (while sequence
      (setf next (car sequence))
      (setf sequence (cdr sequence))
      (setf rules (markov-update-rules rules state next))
      (setf histogram (markov-update-histogram histogram next))
      ; shift next state onto current state list
      (setf state (nconc (cdr state) (list next))))
    ; generalize?
    (cond (generalize
           (setf rule (cons '-> histogram))
           (dotimes (i order)
             (setf rule (cons '* rule)))
           (setf rules (nconc rules (list rule)))))
    rules))


;; ----- WINDOW Class ---------

(setf window-class (send class :new 
                         '(pattern skip-pattern lis cursor)
                         '() pattern-class))

(send window-class :answer :isnew '(p for sk nm tr)
  '((setf pattern p length-pattern for skip-pattern sk name nm trace tr)))


(send window-class :answer :start-period '()
  '((if (null count) (error (format nil "~A, :start-period -- count is null"
                                        name)))
    (cond ((null lis) ;; first time
           (dotimes (i count)
             (push (next pattern) lis))
           (setf lis (reverse lis)))
          (t
           (let ((skip (next skip-pattern)))
             (dotimes (i skip)
               (if lis (pop lis) (next pattern))))
           (setf lis (reverse lis))
           (let ((len (length lis)))
             (while (< len count)
               (incf len)
               (push (next pattern) lis))
             (while (> len count)
               (decf len)
               (pop lis))
             (setf lis (reverse lis)))))
    (setf cursor lis)))


(send window-class :answer :advance '()
  '((send self :set-current (car cursor))
    (pop cursor)))

(defun make-window (pattern length-pattern skip-pattern
                    &key (name "window") trace)
  (send window-class :new pattern length-pattern skip-pattern name trace))

;; SCORE-SORTED -- test if score is sorted
;;
(defun score-sorted (score)
  (let ((result t))
    (while (cdr score)
      (cond ((event-before (cadr score) (car score))
             (setf result nil)
             (return nil)))
      (setf score (cdr score)))
    result))
    

(defmacro score-gen (&rest args)
  (let (key val tim dur (name ''note) ioi trace save 
        score-len score-dur others pre post
        next-expr (score-begin 0) score-end)
    (while (and args (cdr args))
      (setf key (car args))
      (setf val (cadr args))
      (setf args (cddr args))       
      (case key
        (:time (setf tim val))
        (:dur (setf dur val))
        (:name (setf name val))
        (:ioi (setf ioi val))
        (:trace (setf trace val))
        (:save (setf save val))
        (:pre (setf pre val))
        (:post (setf post val))
        (:score-len (setf score-len val))
        (:score-dur (setf score-dur val))
        (:begin (setf score-begin val))
        (:end (setf score-end val))
        (t (setf others (cons key (cons val others))))))
    ;; make sure at least one of score-len, score-dur is present
    (cond ((and (null score-len) (null score-dur))
           (error
           "score-gen needs either :score-len or :score-dur to limit length")))
    ;; compute expression for dur
    (cond ((null dur)
           (setf dur 'sg:ioi)))
    ;; compute expression for ioi
    (cond ((null ioi)
           (setf ioi 1)))
    ;; compute expression for next start time
    (setf next-expr '(+ sg:start sg:ioi))
    ; (display "score-gen" others)
    `(let (sg:seq (sg:start ,score-begin) sg:ioi 
           (sg:score-len ,score-len) (sg:score-dur ,score-dur)
           (sg:count 0) (sg:save ,save) 
           (sg:begin ,score-begin) (sg:end ,score-end) sg:det-end)
       ;; sg:det-end is a flag that tells us to determine the end time
       (cond ((null sg:end) (setf sg:end 0 sg:det-end t)))
       ;; make sure at least one of score-len, score-dur is present
       (loop
         (cond ((or (and sg:score-len (<= sg:score-len sg:count))
                    (and sg:score-dur (<= (+ sg:begin sg:score-dur) sg:start)))
                (return)))
         ,pre
         ,(cond (tim (list 'setf 'sg:start tim)))
         (setf sg:ioi ,ioi)
         (setf sg:dur ,dur)
         (push (list sg:start sg:dur (list ,name ,@others))
               sg:seq)
         ,post
         (cond (,trace
                (format t "get-seq trace at ~A stretch ~A: ~A~%" 
                          sg:start sg:dur (car sg:seq))))
         (incf sg:count)
         (setf sg:start ,next-expr)
         ;; end time of score will be max over start times of the next note
         ;; this bases the score duration on ioi's rather than durs. But
         ;; if user specified sg:end, sg:det-end is false and we do not
         ;; try to compute sg:end.
         (cond ((and sg:det-end (> sg:start sg:end))
                (setf sg:end sg:start))))
       (setf sg:seq (reverse sg:seq))
       ;; avoid sorting a sorted list -- XLisp's quicksort can overflow the
       ;; stack if the list is sorted because (apparently) the pivot points
       ;; are not random.
       (cond ((not (score-sorted sg:seq))
              (setf sg:seq (bigsort sg:seq #'event-before))))
       (push (list 0 0 (list 'SCORE-BEGIN-END ,score-begin sg:end)) sg:seq)
       (cond (sg:save (set sg:save sg:seq)))
       sg:seq)))

;; ============== score manipulation ===========

(defun event-before (a b)
  (< (car a) (car b)))

;; EVENT-END -- get the ending time of a score event
;;
(defun event-end (e) (+ (car e) (cadr e)))

;; EVENT-TIME -- time of an event
;;
(setfn event-time car)

;; EVENT-DUR -- duration of an event
;;
(setfn event-dur cadr)

;; EVENT-SET-TIME -- new event with new time
;;
(defun event-set-time (event time)
  (cons time (cdr event)))


;; EVENT-SET-DUR -- new event with new dur
;;
(defun event-set-dur (event dur)
  (list (event-time event) 
        dur 
        (event-expression event)))
  
  
;; EVENT-SET-EXPRESSION -- new event with new expression
;;
(defun event-set-expression (event expression)
  (list (event-time event) 
        (event-dur event)
        expression))
  
;; EXPR-HAS-ATTR -- test if expression has attribute
;;
(defun expr-has-attr (expression attr)
  (member attr expression))


;; EXPR-GET-ATTR -- get value of attribute from expression
;;
(defun expr-get-attr (expression attr &optional default)
  (let ((m (member attr expression)))
    (if m (cadr m) default)))


;; EXPR-SET-ATTR -- set value of an attribute in expression
;; (returns new expression)
(defun expr-set-attr (expr attr value)
  (cons (car expr) (expr-parameters-set-attr (cdr expr) attr value)))

(defun expr-parameters-set-attr (lis attr value)
  (cond ((null lis) (list attr value))
        ((eq (car lis) attr) (cons attr (cons value (cddr lis))))
        (t (cons (car lis) 
                 (cons (cadr lis) 
                       (expr-parameters-set-attr (cddr lis) attr value))))))


;; EXPR-REMOVE-ATTR -- expression without attribute value pair
(defun expr-remove-attr (event attr)
  (cons (car expr) (expr-parameters-remove-attr (cdr expr) attr)))

(defun expr-parameters-remove-attr (lis attr)
   (cond ((null lis) nil)
         ((eq (car lis) attr) (cddr lis))
         (t (cons (car lis)
                  (cons (cadr lis)
                        (expr-parameters-remove-attr (cddr lis) attr))))))


;; EVENT-GET-ATTR -- get value of attribute from event
;;
(defun event-get-attr (note attr &optional default)
  (expr-get-attr (event-expression note) attr default))


;; EVENT-SET-ATTR -- new event with attribute = value
(defun event-set-attr (event attr value)
  (event-set-expression 
    event
    (expr-set-attr (event-expression event) attr value)))


;; EVENT-REMOVE-ATTR -- new event without atttribute value pair
(defun event-remove-attr (event attr)
  (event-set-expression
     event
     (event-remove-attr (event-expression event) attr)))


;; SCORE-GET-BEGIN -- get the begin time of a score
;;
(defun score-get-begin (score)
  (setf score (score-must-have-begin-end score))
  (cadr (event-expression (car score))))


;; SCORE-SET-BEGIN -- set the begin time of a score
;;
(defun score-set-begin (score time)
  (setf score (score-must-have-begin-end score))
  (cons (list 0 0 (list 'score-begin-end time 
                        (caddr (event-expression (car score)))))
        (cdr score)))


;; SCORE-GET-END -- get the end time of a score
;;
(defun score-get-end (score)
  (setf score (score-must-have-begin-end score))
  (caddr (event-expression (car score))))


;; SCORE-SET-END -- set the end time of a score
;;
(defun score-set-end (score time)
  (setf score (score-must-have-begin-end score))
  (cons (list 0 0 (list 'score-begin-end 
                        (cadr (event-expression (car score))) time))
        (cdr score)))


;; FIND-FIRST-NOTE -- use keywords to find index of first selected note
;;
(defun find-first-note (score from-index from-time)
  (let ((s (cdr score)))
    ;; offset by one because we removed element 0
    (setf from-index (if from-index (max 0 (- from-index 1)) 0))
    (setf from-time (if from-time 
                        (- from-time SCORE-EPSILON)
                        (- SCORE-EPSILON)))
    (if s (setf s (nthcdr from-index s)))
    
    (while (and s (>= from-time (event-time (car s))))
      (setf s (cdr s))
      (incf from-index))
    (1+ from-index)))


;; EVENT-BEFORE -- useful function for sorting scores
;;
(defun event-before (a b)
  (< (car a) (car b)))
  
;; bigsort -- a sort routine that avoids recursion in order
;; to sort large lists without overflowing the evaluation stack
;;
;; Does not modify input list. Does not minimize cons-ing.
;;
;; Algorithm: first accumulate sorted sub-sequences into lists
;; Then merge pairs iteratively until only one big list remains
;; 
(defun bigsort (lis cmp) ; sort lis using cmp function
  ;; if (funcall cmp a b) then a and b are in order
  (prog (rslt sub pairs)
    ;; first, convert to sorted sublists stored on rslt
    ;; accumulate sublists in sub
   get-next-sub
    (if (null lis) (go done-1))
    (setf sub (list (car lis)))
    (setf lis (cdr lis))
   fill-sub
    ;; invariant: sub is non-empty, in reverse order
    (cond ((and lis (funcall cmp (car sub) (car lis)))
           (setf sub (cons (car lis) sub))
           (setf lis (cdr lis))
           (go fill-sub)))
    (setf sub (reverse sub)) ;; put sub in correct order
    (setf rslt (cons sub rslt)) ;; build rslt in reverse order
    (go get-next-sub)
   done-1
    ;; invariant: rslt is list of sorted sublists
    (if (cdr rslt) nil (go done-2))
    ;; invariant: rslt has at least one list
    (setf pairs rslt)
    (setf rslt nil)
   merge-pairs    ;; merge a pair and save on rslt
    (if (car pairs) nil (go end-of-pass)) ;; loop until all pairs merged
    ;; invariant: pairs has at least one list
    (setf list1 (car pairs)) ;; list1 is non-empty
    (setf list2 (cadr pairs)) ;; list2 could be empty
    (setf pairs (cddr pairs))
    (cond (list2
           (setf rslt (cons (list-merge list1 list2 cmp) rslt)))
          (t
           (setf rslt (cons list1 rslt))))
    (go merge-pairs)
   end-of-pass
    (go done-1)
   done-2
    ;; invariant: rslt has one sorted list!
    (return (car rslt))))

(defun list-merge (list1 list2 cmp)
  (prog (rslt)
   merge-loop
    (cond ((and list1 list2)
           (cond ((funcall cmp (car list1) (car list2))
                  (setf rslt (cons (car list1) rslt))
                  (setf list1 (cdr list1)))
                 (t
                  (setf rslt (cons (car list2) rslt))
                  (setf list2 (cdr list2)))))
          (list1
           (return (nconc (reverse rslt) list1)))
          (t
           (return (nconc (reverse rslt) list2))))
    (go merge-loop)))  


;; SCORE-SORT -- sort a score into time order
;;
(defun score-sort (score &optional (copy-flag t)) 
  (setf score (score-must-have-begin-end score))
  (let ((begin-end (car score)))
    (setf score (cdr score))
    (if copy-flag (setf score (append score nil)))
    (cons begin-end (bigsort score #'event-before))))
  

;; PUSH-SORT -- insert an event in (reverse) sorted order
;;
;; Note: Score should NOT have a score-begin-end expression
;;
(defun push-sort (event score)
  (let (insert-after)
    (cond ((null score) (list event))
          ((event-before (car score) event)
           (cons event score))
          (t
           (setf insert-after score)
           (while (and (cdr insert-after) 
                       (event-before event (cadr insert-after)))
             (setf insert-after (cdr insert-after)))
           (setf (cdr insert-after) (cons event (cdr insert-after)))
           score))))


(setf FOREVER 3600000000.0) ; 1 million hours

;; FIND-LAST-NOTE -- use keywords to find index beyond last selected note
;;
;; note that the :to-index keyword is the index of the last note (numbered
;; from zero), whereas this function returns the index of the last note
;; plus one, i.e. selected notes have an index *less than* this one
;;
(defun find-last-note (score to-index to-time)
  ;; skip past score-begin-end event
  (let ((s (cdr score))
        (n 1))
    (setf to-index (if to-index (1+ to-index) (length score)))
    (setf to-time (if to-time (- to-time SCORE-EPSILON)  FOREVER))
    (while (and s (< n to-index) (< (event-time (car s)) to-time))
      (setf s (cdr s))
      (incf n))
    n))


;; SCORE-MUST-HAVE-BEGIN-END -- add score-begin-end event if necessary
;;
(defun score-must-have-begin-end (score)
  (cond ((null score) 
         (list (list 0 0 (list 'SCORE-BEGIN-END 0 0))))
        ((eq (car (event-expression (car score))) 'SCORE-BEGIN-END)
         score)
        (t (cons (list 0 0 (list 'SCORE-BEGIN-END (event-time (car score))
                                 (event-end (car (last score)))))
                 score))))


;; SCORE-SHIFT -- add offset to times of score events
;;
(defun score-shift (score offset &key from-index to-index from-time to-time)
  (setf score (score-must-have-begin-end score))
  (let ((i 1) 
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time))
        (end (caddr (event-expression (car score))))
        result)
    (dolist (event (cdr score))
      (cond ((and (<= start i) (< i stop))
             (setf event (event-set-time 
                          event (+ (event-time event) offset)))
             (setf end (max end (event-end event)))))
      (setf result (push-sort event result))
      (incf i))
    (cons (list 0 0 (list 'SCORE-BEGIN-END
                          (cadr (event-expression (car score)))
                          end))
          (reverse result))))


;; TIME-STRETCH -- map a timestamp according to stretch factor
;;
(defun time-stretch (time stretch start-time stop-time)
  (cond ((< time start-time) time)
        ((< time stop-time) 
         (+ start-time (* stretch (- time start-time))))
        (t ; beyond stop-time
         (+ (- time stop-time) ; how much beyond stop-time
            start-time
            (* stretch (- stop-time start-time))))))
         

;; EVENT-STRETCH -- apply time warp to an event
(defun event-stretch (event stretch dur-flag time-flag start-time stop-time)
  (let* ((new-time (event-time event))
         (new-dur (event-dur event))
         (end-time (+ new-time new-dur)))
    (cond (time-flag
           (setf new-time (time-stretch new-time stretch 
                                        start-time stop-time))))
    (cond ((and time-flag dur-flag)
           ;; both time and dur are stretched, so map the end time just
           ;; like the start time, then subtract to get new duration
           (setf end-time (time-stretch end-time stretch
                                        start-time stop-time))
           (setf new-dur (- end-time new-time)))
          ((and dur-flag (>= new-time start-time) (< new-time stop-time))
           ;; stretch only duration, not time. If note starts in range
           ;; scale to get the new duration.
           (setf new-dur (* stretch new-dur))))
    (list new-time new-dur (event-expression event))))


;; SCORE-STRETCH -- stretch a region of the score
;;
(defun score-stretch (score factor &key (dur t) (time t)
                      from-index to-index (from-time 0) (to-time FOREVER))
  (setf score (score-must-have-begin-end score))
  (let ((begin-end (event-expression (car score)))
        (i 1))
    (if from-index
        (setf from-time (max from-time 
                             (event-time (nth from-index score)))))
    (if to-index
        (setf to-time (min to-time 
                           (event-end (nth to-index score)))))
    ; stretch from start-time to stop-time
    (cons (list 0 0 (list 'SCORE-BEGIN-END 
                          (time-stretch (cadr begin-end) factor 
                                        from-time to-time)
                          (time-stretch (caddr begin-end) factor
                                        from-time to-time)))
          (mapcar #'(lambda (event) 
                      (event-stretch event factor dur time
                                     from-time to-time))
                  (cdr score)))))
    

;; Get the second element of params (the value field) and turn it
;; into a numeric value if possible (by looking up a global variable
;; binding). This allows scores to say C4 instead of 60.
;;
(defun get-numeric-value (params)
  (let ((v (cadr params)))
    (cond ((and (symbolp v) (boundp v) (numberp (symbol-value v)))
           (setf v (symbol-value v))))
    v))

          
(defun params-transpose (params keyword amount)
  (cond ((null params) nil)
        ((eq keyword (car params))
         (let ((v (get-numeric-value params)))
           (cond ((numberp v)
                  (setf v (+ v amount))))
           (cons (car params)
                 (cons v (cddr params)))))
        (t (cons (car params)
                 (cons (cadr params)
                       (params-transpose (cddr params) keyword amount))))))


(defun score-transpose (score keyword amount &key
                        from-index to-index from-time to-time)
  (score-apply score 
               #'(lambda (time dur expression)
                   (list time dur 
                         (cons (car expression)
                               (params-transpose (cdr expression)
                                                 keyword amount))))
               :from-index from-index :to-index to-index
               :from-time from-time :to-time to-time))


(defun params-scale (params keyword amount)
  (cond ((null params) nil)
        ((eq keyword (car params))
         (let ((v (get-numeric-value params)))
           (cond ((numberp v)
                  (setf v (* v amount))))
           (cons (car params)
                 (cons v (cddr params)))))
        (t (cons (car params)
                 (cons (cadr params)
                       (params-scale (cddr params) keyword amount))))))


(defun score-scale (score keyword amount &key
                    from-index to-index from-time to-time)
  (score-apply score 
               #'(lambda (time dur expression)
                   (list time dur
                         (cons (car expression)
                               (params-scale (cdr expression)
                                             keyword amount))))
               :from-index from-index :to-index to-index
               :from-time from-time :to-time to-time))


(defun score-sustain (score factor &key
                      from-index to-index from-time to-time)
  (setf score (score-must-have-begin-end score))
  (let ((i 0)
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time))
        result)
    (dolist (event score)
      (cond ((and (<= start i) (< i stop))
             (setf event (event-set-dur
                          event (* (event-dur event) factor)))))
      (push event result)
      (incf i))
    (reverse result)))


(defun map-voice (expression replacement-list)
  (let ((mapping (assoc (car expression) replacement-list)))
    (cond (mapping (cons (second mapping)
                         (cdr expression)))
          (t expression))))


(defun score-voice (score replacement-list &key
                    from-index to-index from-time to-time)
  (setf score (score-must-have-begin-end score))
  (let ((i 0) 
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time))
        result)
    (dolist (event score)
      (cond ((and (<= start i) (< i stop))
             (setf event (event-set-expression
                          event (map-voice (event-expression event)
                                           replacement-list)))))
      (push event result)
      (incf i))
    (reverse result)))


(defun score-merge (&rest scores)
  ;; scores is a list of scores
  (cond ((null scores) nil)
        (t
         (score-merge-1 (car scores) (cdr scores)))))


;; SCORE-MERGE-1 -- merge list of scores into score
;;
(defun score-merge-1 (score scores)
  ;; scores is a list of scores to merge
  (cond ((null scores) score)
        (t (score-merge-1 (score-merge-2 score (car scores))
                          (cdr scores)))))

;; SCORE-MERGE-2 -- merge 2 scores
;;
(defun score-merge-2 (score addin)
  ;(display "score-merge-2 before" score addin)
  (setf score (score-must-have-begin-end score))
  (setf addin (score-must-have-begin-end addin))
  ;(display "score-merge-2" score addin)
  (let (start1 start2 end1 end2)
    (setf start1 (score-get-begin score))
    (setf start2 (score-get-begin addin))
    (setf end1 (score-get-end score))
    (setf end2 (score-get-end addin))
    
    ;; note: score-sort is destructive, but append copies score
    ;;       and score-shift copies addin
    (score-sort
     (cons (list 0 0 (list 'SCORE-BEGIN-END (min start1 start2)
                           (max end1 end2)))
           (append (cdr score) (cdr addin) nil)))))



;; SCORE-APPEND -- append scores together in sequence
;;
(defun score-append (&rest scores)
  ;; scores is a list of scores
  (cond ((null scores) nil)
        (t
         (score-append-1 (car scores) (cdr scores)))))


;; SCORE-APPEND-1 -- append list of scores into score
;;
(defun score-append-1 (score scores)
  ;; scores is a list of scores to append
  (cond ((null scores) score)
        (t (score-append-1 (score-append-2 score (car scores))
                           (cdr scores)))))


;; SCORE-APPEND-2 -- append 2 scores
;;
(defun score-append-2 (score addin)
  ;(display "score-append-2" score addin)
  (setf score (score-must-have-begin-end score))
  (setf addin (score-must-have-begin-end addin))
  (let (end1 start2 begin-end1 begin-end2)
    (setf start1 (score-get-begin score))
    (setf end1 (score-get-end score))
    (setf start2 (score-get-begin addin))
    (setf end2 (score-get-end addin))
    (setf begin-end1 (event-expression (car score)))
    (setf begin-end2 (event-expression (car addin)))
    (setf addin (score-shift addin (- end1 start2)))
    ;; note: score-sort is destructive, but append copies score
    ;;       and score-shift copies addin
    (score-sort
     (cons (list 0 0 (list 'SCORE-BEGIN-END start1 (+ end1 (- end2 start2))))
           (append (cdr score) (cdr addin) nil)))))


(defun score-select (score predicate &key
                    from-index to-index from-time to-time reject)
  (setf score (score-must-have-begin-end score))
  (let ((begin-end (car score))
        (i 1) 
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time))
        result)
    ;; selected if start <= i AND i < stop AND predicate(...)
    ;; choose if not reject and selected or reject and not selected
    ;; so in other words choose if reject != selected. Use NULL to
    ;; coerce into boolean values and then use NOT EQ to compare
    (dolist (event (cdr score))
      (cond ((not (eq (null reject)
                      (null (and (<= start i) (< i stop)
                                 (or (eq predicate t)
                                     (funcall predicate 
                                      (event-time event) 
                                      (event-dur event) 
                                      (event-expression event)))))))
             (push event result)))
      (incf i))
    (cons begin-end (reverse result))))


;; SCORE-FILTER-LENGTH -- remove notes beyond cutoff time
;;
(defun score-filter-length (score cutoff)
  (let (result)
    (dolist (event score)
      (cond ((<= (event-end event) cutoff)
             (push event result))))
    (reverse result)))


;; SCORE-REPEAT -- make n copies of score in sequence
;;
(defun score-repeat (score n)
  (let (result)
    (dotimes (i n)
      (setf result (score-append result score)))
    result))


;; SCORE-STRETCH-TO-LENGTH -- stretch score to have given length
;;
(defun score-stretch-to-length (score length)
  (let ((begin-time (score-get-begin score))
        (end-time (score-get-end score))
        duration stretch)
    (setf duration (- end-time begin-time))
    (cond ((< 0 duration)
           (setf stretch (/ length (- end-time begin-time)))
           (score-stretch score stretch))
          (t score))))


(defun score-filter-overlap (score)
  (setf score (score-must-have-begin-end score))
  (prog (event end-time filtered-score
         (begin-end (car score)))
    (setf score (cdr score))
    (cond ((null score) (return (list begin-end))))
  loop
    ;; get event from score
    (setf event (car score))
    ;; add a note to filtered-score
    (push event filtered-score)
    ;; save the end-time of this event: start + duration
    (setf end-time (+ (car event) (cadr event)))
    ;; now skip everything until end-time in score
  loop2
    (pop score) ;; move to next event in score
    (cond ((null score) 
           (return (cons begin-end (reverse filtered-score)))))
    (setf event (car score)) ;; examine next event
    (setf start-time (car event))
    ;(display "overlap" start-time (- end-time SCORE-EPSILON))
    (cond ((< start-time (- end-time SCORE-EPSILON))
           ;(display "toss" event start-time end-time)
           (go loop2)))
    (go loop)))


(defun score-print (score)
 (format t "(")
 (dolist (event score)
  (format t "~S~%" event))
 (format t ")~%"))

(defun score-play (score)
  (play (timed-seq score)))


(defun score-adjacent-events (score function &key
                              from-index to-index from-time to-time)
  (setf score (score-must-have-begin-end score))
  (let ((begin-end (car score))
        (a nil)
        (b (second score))
        (c-list (cddr score))
        r newscore
        (i 1)
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time)))
    (dolist (event (cdr score))
      (setf r b)
      (cond ((and (<= start i) (< i stop))
             (setf r (funcall function a b (car c-list)))))
      (cond (r
             (push r newscore)
             (setf a r)))
      (setf b (car c-list))
      (setf c-list (cdr c-list))
      (incf i))
    (score-sort (cons begin-end newscore))))


(defun score-apply (score fn &key
                    from-index to-index from-time to-time)

  (setf score (score-must-have-begin-end score))
  (let ((begin-end (car score))
        (i 1) 
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time))
        result)
    (dolist (event (cdr score))
      (push 
       (cond ((and (<= start i) (< i stop))
              (funcall fn (event-time event)
                          (event-dur event) (event-expression event)))
             (t event))
       result)
      (incf i))
    (score-sort (cons begin-end result))))


(defun score-indexof (score fn &key
                      from-index to-index from-time to-time)
  (setf score (score-must-have-begin-end score))
  (let ((i 1) 
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time))
        result)
    (dolist (event (cdr score))
      (cond ((and (<= start i) (< i stop)
                  (funcall fn (event-time event)
                              (event-dur event)
                              (event-expression event)))
             (setf result i)
             (return)))
      (incf i))
    result))


(defun score-last-indexof (score fn &key
                           from-index to-index from-time to-time)
  (setf score (score-must-have-begin-end score))
  (let ((i 1) 
        (start (find-first-note score from-index from-time))
        (stop (find-last-note score to-index to-time))
        result)
    (dolist (event (cdr score))
      (cond ((and (<= start i) (< i stop)
                  (funcall fn (event-time event)
                           (event-dur event)
                           (event-expression event)))
             (setf result i)))
      (incf i))
    result))


;; SCORE-RANDOMIZE-START -- alter start times with offset
;; keywords: jitter, offset, feel factor
;;
(defun score-randomize-start (score amt &key
                              from-index to-index from-time to-time)
  (score-apply score
               (lambda (time dur expr)
                 (setf time (+ (real-random (- amt) amt) time))
                 (setf time (max 0.0 time))
                 (list time dur expr))))


;; SCORE-READ-SMF -- read a standard MIDI file to a score
;;
(defun score-read-smf (filename)
  (let ((seq (seq-create))
        (file (open-binary filename)))
    (cond (file
           (seq-read-smf seq file)
           (close file)
           (score-from-seq seq))
          (t nil))))


;; SET-PROGRAM-TO -- a helper function to set a list value
(defun set-program-to (lis index value default)
  ;; if length or lis <= index, extend the lis with default
  (while (<= (length lis) index)
    (setf lis (nconc lis (list default))))
  ;; set the nth element
  (setf (nth index lis) value)
  ;; return the list
  lis)


(defun score-from-seq (seq)
  (prog (event tag score programs)
    (seq-reset seq)
loop
    (setf event (seq-get seq))
    (setf tag (seq-tag event))
    (cond ((= tag seq-done-tag)
           (go exit))
          ((= tag seq-prgm-tag)
           (let ((chan (seq-channel event))
                 (when (seq-time event))
                 (program (seq-program event)))
             (setf programs (set-program-to programs chan program 0))
             (push (list (* when 0.001) 1
                         (list 'NOTE :pitch nil :program program))
                   score)))
          ((= tag seq-note-tag)
         (let ((chan (seq-channel event))
                 (pitch (seq-pitch event))
                 (vel (seq-velocity event))
                 (when (seq-time event))
                 (dur (seq-duration event)))
             (push (list (* when 0.001) (* dur 0.001)
                       (list 'NOTE :chan (1- chan) :pitch pitch :vel vel))
                   score))))
    (seq-next seq)
    (go loop)
exit
    (setf *rslt* programs) ;; extra return value
    (return (score-sort score))))


(defun score-write-smf (score filename &optional programs)
  (let ((file (open-binary filename :direction :output))
        (seq (seq-create))
        (chan 1))
    (cond (file
           (dolist (program programs)
             ;; 6 = SEQ_PROGRAM
             (seq-insert-ctrl seq 0 0 6 chan program)
             ;(display "insert ctrl" seq 0 0 6 chan program)
             (incf chan))

           (dolist (event (cdr (score-must-have-begin-end score)))
             (let ((time (event-time event))
                   (dur (event-dur event))
                   (chan (event-get-attr event :chan 0))
                   (pitch (event-get-attr event :pitch))
                   (program (event-get-attr event :program))
                   (vel (event-get-attr event :vel 100)))
               (cond (program
                      ;(display "score-write-smf program" chan program)
                      (seq-insert-ctrl seq (round (* time 1000))
                                       0 6 (1+ chan)
                                       (round program))))
               (cond ((consp pitch)
                      (dolist (p pitch)
                        (seq-insert-note seq (round (* time 1000))
                                         0 (1+ chan) (round p) 
                                         (round (* dur 1000)) (round vel))))
                     (pitch
                      (seq-insert-note seq (round (* time 1000))
                                       0 (1+ chan) (round pitch)
                                       (round (* dur 1000)) (round vel))))))
           (seq-write-smf seq file)
           (close file)))))


;; make a default note function for scores
;;
(defun note (&key (pitch 60) (vel 100))
  ;; load the piano if it is not loaded already
  (if (not (boundp '*piano-srate*)) 
      (abs-env (load "pianosyn")))
  (piano-note-2 pitch vel))

;;================================================================

;; WORKSPACE functions have moved to envelopes.lsp


;; DESCRIBE -- add a description to a global variable
;;
(defun describe (symbol &optional description)
  (add-to-workspace symbol)
  (cond (description
         (putprop symbol description 'description))
        (t
         (get symbol 'description))))

;; INTERPOLATE -- linear interpolation function
;;
;; compute y given x by interpolating between points (x1, y1) and (x2, y2)
(defun interpolate (x x1 y1 x2 y2)
  (cond ((= x1 x2) x1)
        (t (+ y1 (* (- x x1) (/ (- y2 y1) (- x2 (float x1))))))))


;; INTERSECTION -- set intersection
;;
;; compute the intersection of two lists
(defun intersection (a b)
  (let (result)
    (dolist (elem a)
      (if (member elem b) (push elem result)))
    result))

;; UNION -- set union
;;
;; compute the union of two lists
(defun union (a b)
  (let (result)
    (dolist (elem a)
      (if (not (member elem result)) (push elem result)))
    (dolist (elem b)
      (if (not (member elem result)) (push elem result)))
    result))

;; SET-DIFFERENCE -- set difference
;;
;; compute the set difference between two sets
(defun set-difference (a b)
  (remove-if (lambda (elem) (member elem b)) a))

;; SUBSETP -- test is list is subset
;;
;; test if a is subset of b
(defun subsetp (a b)
  (let ((result t))
    (dolist (elem a)
      (cond ((not (member elem b))
             (setf result nil)
             (return nil))))
    result))

;; functions to support score editing in jNyqIDE

(if (not (boundp '*default-score-file*))
    (setf *default-score-file* "score.dat"))

;; SCORE-EDIT -- save a score for editing by jNyqIDE
;;
;; file goes to a data file to be read by jNyqIDE
;; Note that the parameter is a global variable name, not a score,
;; but you do not quote the global variable name, e.g. call
;;    (score-edit my-score)
;;
(defmacro score-edit (score-name)
    `(score-edit-symbol (quote ,score-name)))

(defun score-edit-symbol (score-name)
    (prog ((f (open *default-score-file* :direction :output))
           score expr)
      (cond ((symbolp score-name)
             (setf score (eval score-name)))
            (t
             (error "score-edit expects a symbol naming the score to edit")))
      (cond ((null f)
        (format t "score-edit: error in output file ~A!~%" *default-score-file*)
        (return nil)))

      (format t "score-edit: writing ~A ...~%" *default-score-file*)
      (format f "~A~%" score-name) ; put name on first line
      (dolist (event score) ;cdr scor
        (format f "~A " (event-time event))  ; print start time
        (format f "~A " (event-dur event))   ; print duration

        (setf expr (event-expression event))

        ; print the pitch and the rest of the attributes
        (format f "~A " (expr-get-attr expr :pitch))
        (format f "~A~%" (expr-parameters-remove-attr expr :pitch)))
      (close f)
      (format t "score-edit: wrote ~A events~%" (length score))))


;; Read in a data file stored in the score-edit format and save
;; it to the global variable it came from
(defun score-restore ()
  (prog ((inf (open *default-score-file*))
         name start dur pitch expr score)
    (cond ((null inf)
           (format t "score-restore: could not open ~A~%" *default-score-file*)
           (return nil)))
    (setf name (read inf)) ;; score name
    (loop
      (setf start (read inf))
      (cond ((null start) (return)))
      (setf dur (read inf))
      (setf pitch (read inf))
      (setf expr (read inf))
      (cond (pitch
             (setf expr (expr-set-attr expr :pitch pitch)))))
    (close inf)
    (setf (symbol-value name) score)))