On Wed, May 13, 2009 at 10:52 AM, Jeremy Banks email@example.com wrote:
To someone who's a novice to this, could someone explain to me why it has to be an existing keyword at all? Since not identifiers are valid in that context anyway, why couldn't it be a new keyword that can still be used as an identifier in valid contexts? For example (not that I advocate this choice of keyword at all):
def foo(bar reinitialize_default ): # <-- it's a keyword here reinitialize_default = "It's an identifier here!"
That would be a syntax error now and if it were defined as a keyword only in that context it wouldn't introduce backwards compatibility problems and wouldn't force us to reuse an existing keyword in a context that may be a bit of a stretch.
Is there a reason that this wouldn't be a viable approach?
Traditionally, keywords are recognized at the lexer level, which then passes tokens to the parser. Lexers are pretty simple (typically constants and regular expressions) and don't take the context into account. In principle what you're saying could work, but given the significant reworking of the lexer/parser it would require, it's quite unlikely to happen, for better or for worse.