yes, I admit it's a perler attitude. I still want to know how to do "s///" in haskell. My guess is that for a "real" regex substitution scenario, you would use parsec. Is that more or less correct, or are there other (easier?) approaches. It would of course be great to be able to transfer as much of my PCRE domain experience as possible to haskell. eg in perl: use strict; use warnings; # phone numbers my $strings = [ "123 456 7890", "123 456 7890", "blah", "789 234 1" ]; for my $string ( @$strings ) { my $formatted = tel_num($string); print "$formatted\n" if $formatted; } sub tel_num { my $string = shift or die "no string"; return unless $string =~ /(\d\d\d)\s+(\d\d\d)\s+(\d\d\d\d)/; return "$1-$2-$3" } outputs (not just identified match, prettied up as well): 123-456-7890 123-456-7890 so, best done with parsec, or some other way? Jules Bean wrote:
tphyahoo wrote:
So the core question (speaking as a perler) is how do you write
my $s= 'abcdefg'; $s =~ s/a/z/g; $s =~ s/b/y/g; print "$s\n";
in haskell? There are various haskell regex libraries out there,
But that's such a perler attitude. When all you have is a regex, everything looks like a s///!
This really doesn't look like much of a regex question to me. A more haskelly answer might be as simple as:
m 'a' = 'z' m 'b' = 'y' m x = x
test1 = map m "abcdefg"
...which is general in the sense that 'm' can be an arbitrary function from Char -> Char, and avoids the 'overlapping replace' behaviour alluded to elsewhere in this thread, but is limited if you wanted to do string-based replacement.
To do string-based replacement you do have to think careful about what semantics you're expecting though (w.r.t. overlapping matches, repeated matches, priority of conflicting matches).
Jules _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
-- View this message in context: http://www.nabble.com/trivial-function-application-question-tf2922232.html#a... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.