[Python-Dev] Pragma-style declaration syntax

[M.-A. Lemburg]

Skip Montanaro wrote:
> 
>     MAL> Here are some possible applications of pragmas (just to toss in
>     MAL> a few ideas):
> 
>     MAL> # Cause global lookups to be cached in function's locals for future
>     MAL> # reuse.
>     MAL> pragma globals = 'constant'
> 
>     MAL> # Cause all Unicode literals in the current scope to be
>     MAL> # interpreted as UTF-8.
>     MAL> pragma encoding = 'utf-8'
> 
>     MAL> # Use -OO style optimizations
>     MAL> pragma optimization = 2
> 
>     MAL> # Default division mode
>     MAL> pragma division = 'float'
> 
> Marc-Andre,
> 
> My interpretation of the word "pragma" (and I think a probably common
> interpretation) is that it is a "hint to the compiler" which the compiler
> can ignore if it chooses.  See
> 
>     http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?query=pragma
> 
> Your use of the word suggests that you propose to implement something more
> akin to a "directive", that is, something the compiler is not free to
> ignore.  Ignoring the pragma in the first and third examples will likely
> only make the program run slower.  Ignoring the second or fourth pragmas
> would likely result in incorrect compilation of the source.
> 
> Whatever you come up with, I think the distinction between hint and
> directive will have to be made clear in the documentation.

True, I see the pragma statement as directive. Perhaps its not
the best name after all -- but then it is likely not to be in
use in existing Python programs as identifier, so perhaps we
just need to make it clear in the documentation that some
pragma statements will carry important information, not only hints.

-- 
Marc-Andre Lemburg
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