Jakub Narebski <jnareb@xxxxxxxxx> writes:
> This doesn't work as expected. Map works on _every_ element of list; if
> expression doesn't return anything it just puts undef I think. For example
> while
>
> print join(";",
> map {
> "a/$_" if ($_ eq lc($_))
> } ("a", "b", "C", "d")),
> "\n";'
>
> returns "a/a;a/b;;a/d" (notice the doubled ';'), the correct way would be to
... say this, than using extra grep {}.
print join(";",
map {
($_ eq lc($_)) ? "a/$_" : ()
} ("a", "b", "C", "d")),
"\n";
> What about my proposed solution? Don't sort, use sorted keys instead, i.e.
> something like (after unmangling whitespace)
>
> sub href(%) {
> my @mapping = ( project => "p",
> action => "a",
> hash => "h",
> hash_parent => "hp",
> hash_base => "hb",
> file_name => "f",
> file_parent => "fp",
> page => "pg",
> searchtext => "s",
> );
> my %mapping;
> my @mapping_keys;
> for (my $i = 0; $i < @mapping; $i += 2) {
> my ($k, $v) = ($mapping[$i], $mapping[$i+1]);
> $mapping{$k} = $v;
> push @mapping_keys, $k;
> }
Now this loop got an expensive way to say %mapping = @mapping
plus assigning @mapping_keys, so I would do only the push part
in the loop for readability while changing the name of the
variable a bit more meaningful.
my %mapping = @mapping;
my @valid_params;
for (my $i = 0; $i < @mapping; $i += 2) {
push @valid_params, $mapping[$i];
}
But aside from that, I very much prefer your version that loops
over what _we_ define (i.e. @valid_params), rather than what the
user happens to throw at us (i.e. keys %params).
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