Re: When would you choose foreach instead of map?

[Anonymous Monk]

i use map alot. particulary when morphing data where i expect every input item to produce an output item. alot of code starts like this.

@out =
  <>;
print Dump(@out);

then successive map like stages...

#!/usr/bin/perl -l
use YAML;

# whitespace separated column number of hostnames (base 0)

$col = shift @ARGV || 0;

# hostname  other  junk   -- 0
# other junk hostname junk -- 2
# ...

@out = 
    map { [ join('.', @{$_->[0]}), $_->[1], $_->[2] ] }
    map { [ [ reverse split /\./, $_->[0] ], $_->[1], $_->[2] ] }
    sort { $a->[0] cmp $b->[0] }
    map { [ join( '.', reverse @{$_->[0]} ), [ @{$_->[0]} ], $_->[1] ]
+ }
    map { [ [ split /\./, $_->[0] ], $_->[1] ] }
    map { chomp; @f = split; $f = splice @f, $col, 1; [ $f , [ @f ] ] 
+}
    <>;


# for regular list
print "-" x 50;
for $x ( @out ) {
    print "$x->[0] -- @{$x->[2]}";
}

# for permuted list
print "-" x 50;
for $x ( @out ) {
    for $y ( @{$x->[1]} ) {
        push @{ $d{$y} }, [ $x->[0], $x->[2] ];
    }
}

for $k ( sort keys %d ) {
    print "$k:";
    print "\t$_->[0] -- @{$_->[1]}" for @{ $d{$k} };
}
__END__
order and/or permute hostname with info

cat <<_END_ | perl foo.pl $column
isc.org tra la la la la
juniper.net tra la da la da
paradise.gen.nz bra la da la da
troublemaking.geek.nz bra la la la la
hookup.net woot toot boot
automagic.org bling blang blum
_END_

--------------------------------------------------
hookup.net -- woot toot boot
juniper.net -- tra la da la da
troublemaking.geek.nz -- bra la la la la
paradise.gen.nz -- bra la da la da
automagic.org -- bling blang blum
isc.org -- tra la la la la
--------------------------------------------------
automagic:
    automagic.org -- bling blang blum
geek:
    troublemaking.geek.nz -- bra la la la la
gen:
    paradise.gen.nz -- bra la da la da
hookup:
    hookup.net -- woot toot boot
isc:
    isc.org -- tra la la la la
juniper:
    juniper.net -- tra la da la da
net:
    hookup.net -- woot toot boot
    juniper.net -- tra la da la da
nz:
    troublemaking.geek.nz -- bra la la la la
    paradise.gen.nz -- bra la da la da
org:
    automagic.org -- bling blang blum
    isc.org -- tra la la la la
paradise:
    paradise.gen.nz -- bra la da la da
troublemaking:
    troublemaking.geek.nz -- bra la la la la

i find that when i try to do things like this without map that it gets uglier quicker.

i just dig map. i'm looking forward to Perl6 because i think i can use ==> to reverse the maps

@out = <>
  ==> map { chomp; [ split ] }
  ==> sort { $somthing }
  ==> map { sprintf "blah: @$_" }
  ;

print Dump(@out);