My first Python program -- a lexer
thomas at mlynarczyk-webdesign.de
Sun Nov 9 15:53:01 CET 2008
Arnaud Delobelle schrieb:
> Adding to John's comments, I wouldn't have source as a member of the
> Lexer object but as an argument of the tokenise() method (which I would
> make public). The tokenise method would return what you currently call
> self.result. So it would be used like this.
>>>> mylexer = Lexer(tokens)
At a later stage, I intend to have the source tokenised not all at once,
but token by token, "just in time" when the parser (yet to be written)
accesses the next token:
token = mylexer.next( 'FOO_TOKEN' )
if not token: raise Exception( 'FOO token expected.' )
# continue doing something useful with token
Where next() would return the next token (and advance an internal
pointer) *if* it is a FOO_TOKEN, otherwise it would return False. This
way, the total number of regex matchings would be reduced: Only that
which is expected is "tried out".
But otherwise, upon reflection, I think you are right and it would
indeed be more appropriate to do as you suggest.
Thanks for your feedback.
Ce n'est pas parce qu'ils sont nombreux à avoir tort qu'ils ont raison!
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