my $sorter = sort_by_spec(spec => [
# put odd numbers first, in ascending order
qr/[13579]\z/ => sub { $_[0] <=> $_[1] },
# then put specific numbers here, in this order
4, 2, 42,
# put even numbers last, in descending order
sub { $_[0] % 2 == 0 } => sub { $_[1] <=> $_[0] },
]);
my @res = $sorter->(1..15, 42);
# => (1,3,5,7,9,11,13,15, 4,2,42, 14,12,10,8,6)
DESCRIPTION
This package provides a more powerful alternative to Sort::ByExample.
Unlike in `Sort::ByExample` where you only provide a single array of
example, you can specify multiple examples as well as regex or matcher
subroutine coupled with sort rules. With this, you can more precisely
specify how elements of your list should be ordered. If your needs are
not met by Sort::ByExample, you might want to consider this package.
The downside is performance penalty, especially when your list is
large.
To sort using Sort::BySpec, you provide a "spec" which is an array of
strings, regexes, or coderefs to match against elements of your list to
be sorted. In the simplest form, the spec contains only a list of
examples:
my $sorter = sort_by_spec(spec => ["foo", "bar", "baz"]); # [1]
and this is equivalent to Sort::ByExample:
my $sorter = sbe(["foo", "bar", "baz"]);
You can also specify regex to match elements. This is evaluated after
strings, so this work:
my $sorter = sort_by_spec(spec => [qr/o/, "foo", "bar", "baz", qr/a/]);
my @list = ("foo", "food", "bar", "back", "baz", "fool", "boat");
my @res = $sorter->(@list);
# => ("food","boat","fool", "foo","bar","baz", "back")
Right after a regex, you can optionally specify a sort subroutine to
tell how to sort elements matching that regex, for example:
my $sorter = sort_by_spec(spec => [
qr/o/ => sub { $_[0] cmp $_[1] },
"foo", "bar", "baz",
qr/a/
]);
# the same list @list above will now be sorted into:
# => ("boat","food","fool", "foo","bar","baz", "back")
Note that instead of $a and $b, you should use $_[0] and $_[1]
respectively. This avoids the package scoping issue of $a and $b,
making your sorter subroutine works everywhere without any special
workaround.
Finally, aside from strings and regexes, you can also specify a coderef
matcher for more complex matching:
my $sorter = sort_by_spec(spec => [
# put odd numbers first, in ascending order
sub { $_[0] % 2 } => sub { $_[0] <=> $_[1] },
# then put specific numbers here, in this order
4, 2, 42,
# put even numbers last, in descending order
sub { $_[0] % 2 == 0 } => sub { $_[1] <=> $_[0] },
]);
my @res = $sorter->(1..15, 42);
# => (1,3,5,7,9,11,13,15, 4,2,42, 14,12,10,8,6)
