Set 'quicktions' to optional imports

With b11b213 quicktions was added as a
mandatory requirement to 'mutwo.core'. This happened after the interal
representations of durations were changed from 'floats' to 'fractions':
Afterwards the performance of 'mutwo.core' significantly dropped.

Follow-up commits further improved the performance by using 'floats'
instead of 'fractions' for internal calculations [1]. So the performance
could be much more improved by simply using 'floats' instead of
'fractions' for internal calculations than by replacing 'fractions'
with 'quicktions'. Furthermore nowadays we plan for version
2.0.0 to actually revert the internal representation of durations to
float [2].

Due to these reasons it seems to be better to drop 'quicktions' again as
a mandatory requirement: then 'mutwo' has less dependencies, which
simplifies the installation and the maintenance (these are very important
long-goal terms). The first step to do so is to change the 'mutwo.core' codebase
to only optionally import 'quicktions' in case it has been installed.
The final drop of the 'quicktions' requirement can be done in version
2.0.0.

[1] see for instance fc49bb7
[2] https://github.com/mutwo-org/mutwo.core/blob/7d39b80/ROADMAP.md?plain=1#L4

mutwo/core_constants/__init__.py

@@ -4,9 +4,12 @@
 import fractions
 import typing
 
-import quicktions
+try:
+    import quicktions
+except ImportError:
+    quicktions = None
 
-Real = float | fractions.Fraction | quicktions.Fraction | int
+Real = float | fractions.Fraction | int
 """The main reason for this constant is a mypy issue with Pythons buildin
 [numbers module](https://docs.python.org/3/library/numbers.html) which
 is documented [here](https://github.com/python/mypy/issues/3186). Mypy
@@ -16,6 +19,9 @@
 'float', but this wouldn't include `fractions.Fraction` which is often
 necessary in musical contexts (as github user arseniiv also remarked)."""
 
+if quicktions:
+    Real |= quicktions.Fraction
+
 DurationType = Real
 """Type variable to arguments and return values for `duration`.
 This can be any real number (float, integer, fraction)."""
@@ -24,3 +30,6 @@
 """Type variable to assign to arguments and return values
 which expect objects from the :mod:`mutwo.core.parameters` module,
 but could actually be anything."""
+
+# Cleanup
+del fractions, quicktions, typing

mutwo/core_events/configurations.py

@@ -4,7 +4,17 @@
 import functools
 import typing
 
-import quicktions
+try:
+    import quicktions
+except ImportError:
+    quicktions = None
+
+
+def _add_quicktions(type_tuple: tuple[typing.Type, ...]) -> tuple[typing.Type, ...]:
+    if quicktions:
+        type_tuple += (quicktions.Fraction,)
+    return type_tuple
+
 
 # We can't set core_converters.UnknownObjectToObject
 # directly because it would raise a circular import error.
@@ -22,7 +32,10 @@ def string_to_duration(string: str):
         if "." in string:
             f = float
         elif "/" in string:
-            f = quicktions.Fraction
+            if quicktions:
+                f = quicktions.Fraction
+            else:
+                f = fractions.Fraction
         else:
             f = int
         try:
@@ -34,7 +47,7 @@ def string_to_duration(string: str):
     return core_converters.UnknownObjectToObject[core_parameters.abc.Duration](
         (
             (
-                (float, int, fractions.Fraction, quicktions.Fraction),
+                _add_quicktions((float, int, fractions.Fraction)),
                 core_parameters.DirectDuration,
             ),
             ((str,), string_to_duration),
@@ -110,13 +123,10 @@ def __unknown_object_to_tempo_point():
     from mutwo import core_converters
     from mutwo import core_parameters
 
+    type_tuple = _add_quicktions((float, int, fractions.Fraction))
+
     return core_converters.UnknownObjectToObject[core_parameters.abc.TempoPoint](
-        (
-            (
-                (float, int, fractions.Fraction, quicktions.Fraction),
-                core_parameters.DirectTempoPoint,
-            ),
-        )
+        ((type_tuple, core_parameters.DirectTempoPoint),)
     )
 
 

mutwo/core_parameters/abc.py

@@ -15,8 +15,13 @@
 import operator
 import typing
 
-import quicktions as fractions
-import fractions as _fractions
+try:
+    import quicktions as fractions
+except ImportError:
+    import fractions
+    _fractions = None
+else:
+    import fractions as _fractions
 
 import ranges
 
@@ -251,9 +256,15 @@ class Duration(
     property :attr:`duration` has to be overridden.
 
     The attribute :attr:`duration` is stored in unit `beats`.
+
+    The ``duration`` of :mod:`mutwo` events are therefore not
+    related to a clear physical unit as for instance seconds.
+    The reason for this decision is to simplify musical usage.
     """
 
-    direct_comparison_type_tuple = (float, int, fractions.Fraction, _fractions.Fraction)
+    direct_comparison_type_tuple = (float, int, fractions.Fraction)
+    if _fractions:
+        direct_comparison_type_tuple += (_fractions.Fraction,)
 
     def _math_operation(
         self, other: DurationOrReal, operation: typing.Callable[[float, float], float]