Commit 01a31397 authored by Robert Bradshaw's avatar Robert Bradshaw

minor directive edits

parent 84836476
......@@ -13,28 +13,31 @@ Cython code, unlike Python, must be compiled. This happens in two stages:
* The ``.c`` file is compiled by a C compiler to a ``.so`` file (or a
``.pyd`` file on Windows)
You can tailor the behaviour of the Cython compiler by specifying the
You can tailor the behavior of the Cython compiler by specifying the
directives below.
Compiler directives
====================
Compiler directives are instructions which affect which sort of code
Cython generates. Here is the list:
Compiler directives are instructions which affect the behavior of
Cython code. Here is the list of currently supported directives:
``boundscheck`` (True / False)
If set to False, Cython is free to assume that indexing operations
([]-operator) in the code will not cause any IndexErrors to be
raised. Currently this is only made use of for buffers, but lists
and tuples could be affected in the future. Conditions which would
normally trigger an IndexError may instead cause segfaults or data
corruption if this is set to False. Default is True.
raised. Currently this is only made use of for buffers, lists and
tuples, but could be affected other types in the future. Conditions
which would normally trigger an IndexError may instead cause
segfaults or data corruption if this is set to False.
Default is True.
``wraparound`` (True / False)
In Python arrays can be indexed relative to the end. For example
A[-1] indexes the last value of a list. In C negative indexing is
not supported. If set to False, Cython will not ensure that python
indexing is not used. Default is True.
not supported. If set to False, Cython will neither check for nor
correctly handle negative indices, possibly causing segfaults or
data corruption.
Default is True.
``nonecheck`` (True / False)
If set to False, Cython is free to assume that native field
......@@ -55,7 +58,7 @@ Cython generates. Here is the list:
If set to False, Cython will adjust the remainder and quotient
operators C types to match those of Python ints (which differ when
the operands have opposite signs) and raise a
``ZeroDivisionError`` when the right operand is 0. This has about
``ZeroDivisionError`` when the right operand is 0. This has up to
a 35% speed penalty. If set to True, no checks are performed. See
`CEP 516 <http://wiki.cython.org/enhancements/division>`_. Default
is False.
......@@ -79,7 +82,8 @@ Cython generates. Here is the list:
``infer_types`` (True / False)
Infer types of untyped variables in function bodies. Default is
False.
None, indicating that on safe (semantically-unchanging) inferences
are allowed.
How to set directives
---------------------
......@@ -108,7 +112,6 @@ Locally
For local blocks, you need to cimport the special builtin ``cython``
module::
#!python
cimport cython
Then you can use the directives either as decorators or in a with
......
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