[Rio-pm] [Golf] Função drop Haskell

[Nilson Santos Figueiredo Jr.]

Uma solução, warnings and strict compliant:

sub drop {
    my ($n, $w) = @_;
    $n = 0 if $n < 0;
    return ( $n > length $w ? '' : substr($w,$n) ) if !ref $w;
    @$w[$n..$#{$w}];
}

Se colocar tudo em uma linha:

sub drop{my($n,$w)=@_;$n=0
if$n<0;return($n>length$w?'':substr($w,$n))if!ref$w;@$w[$n..$#{$w}];}

96 caracteres. Deve dar pra melhorar bastante ainda. Se tirar o "my"
pra deixar de ser strict compliant, cai pra 94.

-Nilson

2010/2/3 Daniel de Oliveira Mantovani <daniel.oliveira.mantovani at gmail.com>:
> Olá pessoal, o desafio envolve a função drop do Haskell:
>
> <haskell>
> ghci> myDrop 2 "foobar"
> "obar"
> ghci> myDrop 4 "foobar"
> "ar"
> ghci> myDrop 4 [1,2]
> []
> ghci> myDrop 0 [1,2]
> [1,2]
> ghci> myDrop 7 []
> []
> ghci> myDrop (-2) "foo"
> "foo"
> </haskell>
>
> Eu fiz em Perl, para ficar claro:
>
> <perl>
> sub drop {
>    my ( $n, $xs ) = @_;
>    if ( ref $_[1] ne 'ARRAY' ) {
>        $n <= 0 ? return $_[1] : return substr( $_[1], $n );
>    }
>    if ( $n <= 0 || !@_ ) {
>        return @{$xs};
>    }
>    else {
>        shift @{$xs};
>        drop( ( $n - 1 ), $xs );
>    }
> }
> </perl>
>
> Exemplos:
> mantovani at mantovani-desktop:~/Perl/Funcional$ perl -MHaskell -E 'say
> $_ for drop(3,[1,2,3,4,5,6])'
> 4
> 5
> 6
>
> mantovani at mantovani-desktop:~/Perl/Funcional$ perl -MHaskell -E 'say
> $_ for drop(1,"ofernandoagoragolf")'
> fernandoagoragolf
>
> mantovani at mantovani-desktop:~/Perl/Funcional$ perl -MHaskell -E 'say
> $_ for drop(2,["mantovani","garu","fernando","blabos"])'
> fernando
> blabos
>
> mantovani at mantovani-desktop:~/Perl/Funcional$ perl -MHaskell -E 'say
> $_ for drop(-1,["mantovani","garu","fernando","blabos"])'
> mantovani
> garu
> fernando
> blabos
>
> mantovani at mantovani-desktop:~/Perl/Funcional$ perl -MHaskell -E 'say
> $_ for drop(-1,"mantovani")'
> mantovani
>
> mantovani at mantovani-desktop:~/Perl/Funcional$ perl -MHaskell -E 'say
> $_ for drop(10,"mantovani")'
>
> --
> "If you’ve never written anything thoughtful, then you’ve never had
> any difficult, important, or interesting thoughts. That’s the secret:
> people who don’t write, are people who don’t think."
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