Feedback welcome on the below set of conventions -- I just picked some
conventions to get going and implemented them as they are easily
changeable. So feel free to comment on all choices of names, letters etc.
Terminology first -- I don't really like the word pragma... "code
generation options" are perhaps better? I've called them "(compiler)
options" below and in the code base, while calling what is options today
"arguments" (as it is command line arguments they really are).
Anyway, the system is this: Options.py contains a list of compiler
options to be controlled through this system. Currently this is only a
boolean "boundscheck".
ALL options we define can then consistently be toggled in the four ways
listed below. During a transform step, ALL nodes in the parse tree has a
node.options dictionary added giving all options (with defaults filled
in) in effect for that exact node (this only adds a reference of course,
so consider that dict immutable).
IndexNode then simply checks self.options['boundscheck'].
Ways to set options:
a)
#cython: boundscheck=True, other=False
#cython: third = no
before any code in the file (but whitespace is allowed, I'm using
Plex/the parser). The boolean value is case-insensitive and
true/false/yes/no is allowed (is this too much? The thing is, for
command-line arguments "True" is rather unfriendly and I'd like it to be
consistent).
b) A command line argument "cython -O boundscheck=False,other=tRUe -O
third=yes". This overrides the #cython comments, but NOT c) and d)
listed below.
The syntax of the string passed to -O is the same as the one passed to
#cython, which is why I allowed yes/no in it. (For instance, ssh has
options like this: ssh -o ForwardX11=no).
c) A decorator works on function-scope:
cimport cython
@cython.boundscheck(True)
def f():
...
The decorator is stripped away before the decorator transform. There is
not really such symbol as cython.boundscheck in the scope, it is a magic
option only. So of course you cannot do
a = cython.boundscheck
@a
...
d) A with statement:
cimport cython
with cython.boundscheck(False):
...
The entire with statement is then stripped out of the source prior to
the with transformation.
BTW, on "cimport cython": This is magic as well. I.e. it always is in
front of the include path, and there will be no way to have a pxd file
named "cython.pxd" imported. Is this OK? (I can change it but it would
be less simple in more than one place, and people really should always
have the cython scope available.)
--
Dag Sverre
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