Re: compiling case insensitive regular expressions

"glen herrmannsfeldt" <gah@ugcs.caltech.edu> a icrit dans le message de
> Armel <armelasselin@hotmail.com> wrote:
>> I need to compile regular expressions which are case insensitive,
>> [..]
> Another way [...] is to supply a bit mask for
> each character being compared. Only bits with a '1' in the mask are
> used in the comparison.


I used that technic to build a LL(1) based Z80 disassembler/decompiler years
ago, to decode "structural bits" (vs. values bits) in instructions, but I
don't think its applicable to a AFD-based regular expression engine, before
knowing which bits can be ignored the AFD will first need to determine a
class for the character. it will simply result in a "tolower(c)" (or
toupper(c) ) called on each character of the input, but expressed and coded
in another way. The preparation phase still has to verify that there are no
two paths leaving a state with 'a' and 'A' for example (as they would become
a single path once the mask applied).


it would advocate in favor of the tolower( ) solution.


Regards
Armel

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