Please take this to python-ideas. On Fri, Mar 27, 2009 at 2:15 PM, Joe Smith <unknown_kev_...@hotmail.com> wrote: > > Jared Grubb wrote: >> >> I'm not a EBNF expert, but it seems that we could modify the grammar to >> be more restrictive so the above code would not be silently valid. E.g., >> "++5" and "1+++5" and "1+-+5" are syntax errors, but still keep "1++5", >> "1+-5", "1-+5" as valid. (Although, '~' throws in a kink... should '~-5' be >> legal? Seems so...) > > So you want something like > u_expr :: = > power | "-" xyzzy_expr | "+" xyzzy_expr | "\~" u_expr > xyzzy_expr :: = > power | "\~" u_expr > > Such that: > 5 # valid u_expr > +5 # valid u_expr > -5 # valid u_expr > ~5 # valid u_expr > ~~5 # valid u_expr > ~+5 # valid u_expr > +~5 # valid u_expr > ~-5 # valid u_expr > -~5 # valid u_expr > +~-5# valid u_expr > > ++5 # not valid u_expr > +-5 # not valid u_expr > -+5 # not valid u_expr > --5 # not valid u_expr > > While, I'm not a python developer, (just a python user) that sounds > reasonable to me, as long as this does not silently change the meaning of > any expression, but only noisily breaks programs, and that the broken > constructs are not used frequently. > > Can anybody come up with any expressions that would silently change in > meaning if the above were applied? > > Obviously a sane name would need to be chosen to replace xyzzy_expr. > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/guido%40python.org >
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