in reply to Mapping elements returned from a grep statement

This worked fine for me: 

@array = (['EMBL','a','b'],['c','d'],['EMBL','e','f']);
$list = join "\n", map {${$_}[1],${$_}[2]}grep { ${$_}[0] eq "EMBL" } 
+@array;
print $list;

[download]
This prints 'abef' separated by newlines.

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Re: Re: about grep....
by demerphq (Chancellor) on Jan 17, 2002 at 16:44 UTC
    Hi. While your solution appears to be correct the syntax you have chosen is, well, odd enough that I went cross-eyed trying to read it..

    So heres my simplification 

    #Initial code...
@array = (['EMBL','a','b'],['c','d'],['EMBL','e','f']);
$list = join "\n", map {${$_}[1],${$_}[2]}grep { ${$_}[0] eq "EMBL" } 
+@array;
print $list;

#first step convert the ${$_}[$index] to $_->[$index]

$list = join "\n", map { $_->[1],$_->[2] } grep { $_->[0] eq "EMBL" } 
+@array;

#second step convert to list slice

$list = join "\n", map { @{$_}[1,2] } grep { $_->[0] eq "EMBL" } @arra
+y;

#next step simplify map{}grep{} into just map{}

$list = join "\n", map { $_->[0] eq "EMBL" ? @{$_}[1,2] : () }  @array
+;

print "\nSimplified:\n$list";

    [download]
    Usually (yes there are exceptions) map {} grep{} or grep{} map{} can be simplified into 
    map { (grep_condition) ? map_function : () }

    [download]
    With greater efficiency and easier understanding (er on the latter IMO :-).

    Yves / DeMerphq
    --
    When to use Prototypes?

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