apertium-tools/apertium-tolk/simplegeneric.py

   1 __all__ = ["generic"]
   2
   3 from types import ClassType, InstanceType
   4 classtypes = type, ClassType
   5
   6 def generic(func):
   7     """Create a simple generic function"""
   8
   9     _sentinel = object()
  10
  11     def _by_class(*args, **kw):
  12         cls = args[0].__class__
  13         for t in type(cls.__name__, (cls,object), {}).__mro__:
  14             f = _gbt(t, _sentinel)
  15             if f is not _sentinel:
  16                 return f(*args, **kw)
  17         else:
  18             return func(*args, **kw)
  19
  20     _by_type = {object: func, InstanceType: _by_class}
  21     _gbt = _by_type.get
  22
  23     def when_type(t):
  24         """Decorator to add a method that will be called for type `t`"""
  25         if not isinstance(t, classtypes):
  26             raise TypeError(
  27                 "%r is not a type or class" % (t,)
  28             )
  29         def decorate(f):
  30             if _by_type.setdefault(t,f) is not f:
  31                 raise TypeError(
  32                     "%r already has method for type %r" % (func, t)
  33                 )
  34             return f
  35         return decorate
  36
  37
  38
  39
  40
  41
  42     _by_object = {}
  43     _gbo = _by_object.get
  44
  45     def when_object(o):
  46         """Decorator to add a method that will be called for object `o`"""
  47         def decorate(f):
  48             if _by_object.setdefault(id(o), (o,f))[1] is not f:
  49                 raise TypeError(
  50                     "%r already has method for object %r" % (func, o)
  51                 )
  52             return f
  53         return decorate
  54
  55
  56     def dispatch(*args, **kw):
  57         f = _gbo(id(args[0]), _sentinel)
  58         if f is _sentinel:
  59             for t in type(args[0]).__mro__:
  60                 f = _gbt(t, _sentinel)
  61                 if f is not _sentinel:
  62                     return f(*args, **kw)
  63             else:
  64                 return func(*args, **kw)
  65         else:
  66             return f[1](*args, **kw)
  67
  68     dispatch.__name__       = func.__name__
  69     dispatch.__dict__       = func.__dict__.copy()
  70     dispatch.__doc__        = func.__doc__
  71     dispatch.__module__     = func.__module__
  72
  73     dispatch.when_type = when_type
  74     dispatch.when_object = when_object
  75     dispatch.default = func
  76     dispatch.has_object = lambda o: id(o) in _by_object
  77     dispatch.has_type   = lambda t: t in _by_type
  78     return dispatch
  79
  80
  81
  82
  83 def test_suite():
  84     import doctest
  85     return doctest.DocFileSuite(
  86         'README.txt',
  87         optionflags=doctest.ELLIPSIS|doctest.REPORT_ONLY_FIRST_FAILURE,
  88     )
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