Add documentation for the (nonlocal ...) directive

Signed-off-by: Gregor Best <gbe@unobtanium.de>
This commit is contained in:
Gregor Best 2015-05-11 23:38:02 +02:00
parent 685688f04c
commit 9ed9bc5e11

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@ -1008,6 +1008,29 @@ conditional expression. Some examples:
[0, 2, 4, 6, 8]
nonlocal
--------
``nonlocal`` can be used to mark a symbol as not local to the current scope.
The parameters are the names of symbols to mark as nonlocal. This is necessary
to modify variables through nested ``let`` scopes:
.. code-block:: clj
(let [[x 0]]
(for [y (range 10)]
(let [[z (inc y)]]
(nonlocal x) ; allow the setv to "jump scope" to resolve x
(setv x (+ x y))))
x)
Without the call to ``(nonlocal x)``, this code would result in an
UnboundLocalError being raised during the call to ``setv``. This is the result
of the way Python handles scoping for nested functions, which are used by Hy to
implement ``let``. See `PEP3104 <https://www.python.org/dev/peps/pep-3104/>`_
for further information.
not
---