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Can you identify token separators, and break the input up into stuff which isn't a problem, and stuff which might be ?

Starting by tidying up:

$query =~ s/\s+/ /g ; # that's the whitespace $query =~ s/\A\s// ; # strip leading $query =~ s/\s\Z// ; # strip trailing $query = lc($query) ; # all lower case $query =~ s/(["'])((?:\\\1|\1\1|.)*?)\1/mash_s($1, $2)/eg ; # Eliminate separators from quoted string +s sub mash_s { my ($q, $s) = @_ ; $s =~ tr/0-9a-z/\\/c ; return $q.$s.$q ; } ;
which, in particular, leaves all "..." or '...' strings containing only [0-9a-z\\]. Means that can then attack anything between separator characters:
$query =~ s/([^ !#\$%()*,\/:;<=>?\@[\]^{|}~]+)/mash_l($1)/eg ; sub mash_l { my ($s) = @_ ; return $s if $s =~ /^(?:[a-z]+|\+|\-)$/ ; return 'N' if $s =~ /^[+-]?(?: (?:\d+(?:\.\d*)? | \.\d+) (?:e[+-]\d+ +)? |(?:0(?: x[0-9a-f]+ |b[01]+ ) ) |x'[0-9a-f]+' |b'[01]+' )$/x ; return 'S' if $s =~ /^(["']).*?\1$/ ; return $s ; } ;
Sadly, what this shows most clearly is that distinguishing unary and binary '+' and '-' is tricky. The above will cope with 12 + -17 and 12*-5, but will fail on 12+13 or 12 +-13 and so on...

...using a parser, where somebody else has done all the hard work, looks like a good trick !

In reply to Re^3: In search of an efficient query abstractor by gone2015
in thread In search of an efficient query abstractor by xaprb

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