Re^2: Is it possible to sort using a coderef, without first storing the coderef in a scalar

The part that I'm not quite sure about is the distinction between these two:

# Doesn't work
sort \&numeric @list;

# Works
my $sorter = \&numeric; 
sort $sorter @list;
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I know that the first example would work if I used numeric instead of \&numeric - but why does \&numeric not also work?

I'm playing with a module that defines a set of common sort patterns, and provides methods that return coderefs that implement the pattern that was requested.

For example, sorting a list of hashes based on the value of a user specified key. The custom implementation would be something like:

sub sort_hashkey($$) {
    my ($a,$b) = @_;
    $a->{foo} <=> $b->{foo};
}

my @sorted = sort_hashkey @list;
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My module provides this:

my $sorter = sorthash_numeric('foo');
my @sorted = sort $sorter @list;
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It would be nice, but not neccesary, to do this:

my @sorted = sort sorthash_alpha('foo') @list;
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Comment on Re^2: Is it possible to sort using a coderef, without first storing the coderef in a scalar Select or Download Code

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Re^3: Is it possible to sort using a coderef, without first storing the coderef in a scalar by ikegami (Patriarch) on Jul 26, 2006 at 05:38 UTC
If you wish to use that syntax, you could use a wrapper. `sub mysort { my $sorter = shift; return sort $sorter @_; } my @sorted = mysort sorthash_alpha('foo'), @list;` [download]	[reply] [d/l]
Re^3: Is it possible to sort using a coderef, without first storing the coderef in a scalar by davido (Cardinal) on Jul 26, 2006 at 05:33 UTC
Because you have a choice according to the docs for sort. You can use a block, a subname, or (from the docs): "SUBNAME may be a scalar variable name (unsubscripted), in which case the value provides the name of (or a reference to) the actual subroutine to use." There is nothing in the docs that says you can use a subroutine call to return a sub reference. You can use a block, a subname, or a scalar variable containing the name of a sub or a reference to a sub. Nothing else. And your sub named in 'subname' must return an integer (-1, 0 or 1, for example). Likewise, the sub referred to in $subname must return an integer. Dave	[reply]