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generator/solo/groups.py

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+"""Exact rhythmic groups for generated material; imported music is not quantized.
+
+Binary boundaries may be displaced together. Tuplet runs must return to their
+entry subdivision phase before binary material resumes. A search boundary is
+not a rhythmic boundary and must not be used to clip a group.
+"""
+from __future__ import annotations
+import dataclasses
+from fractions import Fraction as F
+
+
+@dataclasses.dataclass(frozen=True)
+class RhythmGroup:
+  start: F
+  end: F
+  family: str
+  events: tuple[tuple[F, F], ...]
+  displacement: F = F()
+  source: str = ''
+
+
+def describe(pattern, *, origin=F(), source='', imported=False):
+  if not pattern:return ()
+  if imported:
+    return (RhythmGroup(origin, origin+pattern[-1][1], 'source', pattern, source=source),)
+  result=[]; i=0
+  while i<len(pattern):
+    a,b=pattern[i]
+    if b<=a or i and a<pattern[i-1][1]:raise ValueError('overlapping rhythm group')
+    # A complete ternary figure can be intentionally displaced on an eighth.
+    if (b-a).denominator%3==0:
+      if (a*2).denominator!=1:raise ValueError('unexplained tuplet entry phase')
+      start=i; cursor=a
+      while i<len(pattern):
+        x,y=pattern[i]
+        if x!=cursor or (y-x).denominator not in (3,6):break
+        cursor=y;i+=1
+        if (cursor-a).denominator==1:break
+      if i==start or (cursor-a).denominator!=1:
+        raise ValueError('incomplete tuplet group')
+      group=pattern[start:i]
+      result.append(RhythmGroup(origin+a,origin+cursor,'triplet',group,a%1,source))
+    else:
+      if (a*4).denominator!=1 or (b*4).denominator!=1:
+        raise ValueError('unexplained binary subdivision phase')
+      family='sixteenth' if (a*2).denominator!=1 or (b*2).denominator!=1 else 'binary'
+      result.append(RhythmGroup(origin+a,origin+b,family,((a,b),),a%1,source));i+=1
+  return tuple(result)
+
+
+def valid(pattern):
+  try:describe(pattern);return True
+  except ValueError:return False
+
+
+def signature(notes):
+  """Translation-invariant duration, inter-onset and rest vocabulary."""
+  return tuple((n.end-n.start, notes[i+1].start-n.end if i+1<len(notes) else F())
+    for i,n in enumerate(notes))
+
+
+def broaden(pattern, arrival, release):
+  """Reopen an editable binary tail; never slice a tuplet or inherit its phase."""
+  if (arrival*2).denominator!=1 or (release*2).denominator!=1:return ()
+  for group in describe(pattern):
+    if group.family=='triplet' and group.start<arrival<group.end:return ()
+  result=tuple((a,min(b,arrival)) for a,b in pattern if a<arrival)+((arrival,release),)
+  return result if valid(result) else ()