How can I use MAP to increment values in an array?
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From: Mr P on 10 May 2010 15:44 I have an array in which I want to add a counter - for example, change CAT to CAT #: ....so CAT DOG CAT MOUSE EEL CAT becomes CAT 1 DOG CAT 2 MOUSE EEL CAT 3 Obviously I can write a little loop like my $c = 0; for ( @a ) { next unless /^CAT/; $c++; # wow that's weird $_ .= " $c"; } But what I'd prefer is something like my $c = 1; map s/^(CAT)/$1 $c++/e, @a; I read and read on this, and I also tried: map s/^(CAT)/$1 $c++/e, @a; since it appeared that within the RHS of the s///, a single + was an increment operator. Am I in the ballpark here guys? Everything I've tried results in interpreter errors. Thanks, MP
From: Mr P on 10 May 2010 15:45 On May 10, 3:44 pm, Mr P <misterp...(a)gmail.com> wrote: > I have an array in which I want to add a counter - for example, change > CAT to CAT #: > > ...so > CAT > DOG > CAT > MOUSE > EEL > CAT > > becomes > CAT 1 > DOG > CAT 2 > MOUSE > EEL > CAT 3 > > Obviously I can write a little loop like > > my $c = 0; > for ( @a ) > { > next unless /^CAT/; > $c++; # wow that's weird > $_ .= " $c"; > } > > But what I'd prefer is something like > > my $c = 1; > map s/^(CAT)/$1 $c++/e, @a; > > I read and read on this, and I also tried: > map s/^(CAT)/$1 $c++/e, @a; > > since it appeared that within the RHS of the s///, a single + was an > increment operator. > > Am I in the ballpark here guys? Everything I've tried results in > interpreter errors. > > Thanks, > MP oops I mean I ALSO TRIED s/^(CAT)/$1 $c+/e, @a; # single +
From: Uri Guttman on 10 May 2010 15:53 >>>>> "P" == P <misterperl(a)gmail.com> writes: P> my $c = 0; P> for ( @a ) P> { P> next unless /^CAT/; P> $c++; # wow that's weird wierd in what way? P> $_ .= " $c"; P> } P> But what I'd prefer is something like P> my $c = 1; P> map s/^(CAT)/$1 $c++/e, @a; that won't work. the replacement is an expression with /e. you are thinking it is a string AND an expression. so make an expression (multiple statements are allowed) with the last one being the replacement value. something like this: (untested) s/^(CAT)/$c++ ; "$1 $c:/e foreach @a; and don't use map without returning a list. foreach modifier is better for that. P> I read and read on this, and I also tried: P> map s/^(CAT)/$1 $c++/e, @a; P> since it appeared that within the RHS of the s///, a single + was an P> increment operator. huh?? P> Am I in the ballpark here guys? Everything I've tried results in P> interpreter errors. well, everything you tried is a syntax error. as i said, the code in the replacement part must be a valid expression under /e. this by itself is not valid perl: $1 $c++ uri -- Uri Guttman ------ uri(a)stemsystems.com -------- http://www.sysarch.com -- ----- Perl Code Review , Architecture, Development, Training, Support ------ --------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------
From: Dr.Ruud on 10 May 2010 16:00 Mr P wrote: > I have an array in which I want to add a counter - for example, change > CAT to CAT #: > > ....so > CAT > DOG > CAT > MOUSE > EEL > CAT > > becomes > CAT 1 > DOG > CAT 2 > MOUSE > EEL > CAT 3 perl -MData::Dumper -wle' my (@r, %c); push @r, [$_, ++$c{$_}] for qw/ CAT DOG CAT MOUSE EEL CAT /; print Dumper(\@r); ' -- Ruud
From: Dr.Ruud on 10 May 2010 16:11
Dr.Ruud wrote: > Mr P wrote: >> I have an array in which I want to add a counter - for example, change >> CAT to CAT #: >> >> ....so >> CAT >> DOG >> CAT >> MOUSE >> EEL >> CAT >> >> becomes >> CAT 1 >> DOG >> CAT 2 >> MOUSE >> EEL >> CAT 3 > > perl -MData::Dumper -wle' > my (@r, %c); > push @r, [$_, ++$c{$_}] > for qw/ CAT DOG CAT MOUSE EEL CAT /; > print Dumper(\@r); > ' And use %c to decide whether you want to print the "1". perl -MData::Dumper -wle' my (@r, %c, $k); push @r, [$_, ++$c{$_}] for qw/ CAT DOG CAT MOUSE EEL CAT /; print $k=$_->[0], $c{$k}>1 ? " $_->[1]" : "" for @r; ' CAT 1 DOG CAT 2 MOUSE EEL CAT 3 -- Ruud |