| Trivial Generic Functions |
Trivial Generic Functions |
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========================= |
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(NEW in 0.6: `Inspection and Extension`_, and thread-safe method registration.) |
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| The ``simplegeneric`` module lets you define simple single-dispatch |
The ``simplegeneric`` module lets you define simple single-dispatch |
| generic functions, akin to Python's built-in generic functions like |
generic functions, akin to Python's built-in generic functions like |
| ``len()``, ``iter()`` and so on. However, instead of using |
``len()``, ``iter()`` and so on. However, instead of using |
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... |
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Inspection and Extension |
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------------------------ |
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You can find out if a generic function has a method for a type or object using |
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the ``has_object()`` and ``has_type()`` methods:: |
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>>> move.has_object(zig) |
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True |
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>>> move.has_object(42) |
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False |
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>>> move.has_type(X) |
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True |
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>>> move.has_type(float) |
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False |
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Note that ``has_type()`` only queries whether there is a method registered for |
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the *exact* type, not subtypes or supertypes:: |
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>>> class Z(X): pass |
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>>> move.has_type(Z) |
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False |
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You can create a generic function that "inherits" from an existing generic |
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function by calling ``generic()`` on the existing function:: |
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>>> move2 = generic(move) |
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>>> move(2101, "war") |
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In AD 2101, war was beginning. |
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Any methods added to the new generic function override *all* methods in the |
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"base" function:: |
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>>> @move2.when_type(X) |
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... def move2_X(item, target): |
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... print "You have no chance to survive make your %s!" % (target,) |
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>>> move2(X(), "time") |
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You have no chance to survive make your time! |
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>>> move2(Y(), "time") |
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You have no chance to survive make your time! |
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Notice that even though ``move()`` has a method for type ``Y``, the method |
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defined for ``X`` in ``move2()`` takes precedence. This is because the |
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``move`` function is used as the ``default`` method of ``move2``, and ``move2`` |
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has no method for type ``Y``:: |
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>>> move2.default is move |
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True |
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>>> move.has_type(Y) |
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True |
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>>> move2.has_type(Y) |
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False |
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| Limitations |
Limitations |
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----------- |
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Diff of /simplegeneric/README.txt
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