Merge pull request #803 from farhaven/nonlocal-doc
Add documentation for the (nonlocal ...) directive
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@ -1024,6 +1024,44 @@ conditional expression. Some examples:
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[0, 2, 4, 6, 8]
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nonlocal
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--------
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.. versionadded:: 0.11.1
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**PYTHON 3.0 AND UP ONLY!**
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``nonlocal`` can be used to mark a symbol as not local to the current scope.
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The parameters are the names of symbols to mark as nonlocal. This is necessary
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to modify variables through nested ``let`` or ``fn`` scopes:
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.. code-block:: clj
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(let [[x 0]]
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(for [y (range 10)]
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(let [[z (inc y)]]
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(nonlocal x) ; allow the setv to "jump scope" to resolve x
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(setv x (+ x y))))
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x)
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(defn some-function []
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(let [[x 0]]
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(register-some-callback
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(fn [stuff]
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(nonlocal x)
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(setv x stuff)))))
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In the first example, without the call to ``(nonlocal x)``, this code would
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result in an UnboundLocalError being raised during the call to ``setv``.
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In the second example, without the call to ``(nonlocal x)``, the inner function
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would redefine ``x`` to ``stuff`` inside its local scope instead of overwriting
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the ``x`` in the outer function
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See `PEP3104 <https://www.python.org/dev/peps/pep-3104/>`_ for further
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information.
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not
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---
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