Help language development. Donate to The Perl Foundation

Deepgrep cpan:ELCARO last updated on 2021-01-26

Deepgrep-0.1.2/

NAME

Deepgrep - Grep elements inside nested iterables.

SYNOPSIS

use Deepgrep;

my @xs = (
    [< a  b  c  d >],
    [< e  f* g  h >],
    [< i  j* k  l >],
    [< m  n  o  p >],
);

say deepgrep(@xs, *.ends-with('*')).raku;
# ("f*", "j*").Seq

say deepgrep(@xs, *.ends-with('*'), :k).raku;
# ((1, 1), (2, 1)).Seq

say deepgrep(@xs, *.ends-with('*'), :kv).raku;
# ((1, 1), "f*", (2, 1), "j*").Seq

say deepgrep(@xs, *.ends-with('*'), :p).raku;
# ((1, 1) => "f*", (2, 1) => "j*").Seq

NOTES

Similar to deepmap, this function will descend into Iterables. It returns a flattened list of values that match the given predicate.

You might think that like deepmap, the nesting structure should be maintained, but that functionality can already be achieved with deepmap

say @xs.deepmap(-> $x { $x if $x.ends-with('*') }).raku;
# [[], ["f*"], ["j*"], []]

However deepmap cannot return keys (indices), or pairs, etc. Getting the indicies is useful if you want to modify deeply nested mutable elements in-place

for deepgrep(@xs, *.ends-with('*'), :k) -> ($x, $y) {
    @xs[$x;$y] .= chop
}

This extends down to deeper nested structures as expected

my @zs = [
    [
        ['a', 'b'], ['c', 'd'],
        ['e', 'F'], ['g', 'h'],
    ],
    [
        ['i', 'J'], ['k', 'l'],
        ['m', 'n'], ['o', 'p'],
    ]
];

for @zs.&deepgrep(/<:Lu>/, :k) -> ($x, $y, $z) {
    @zs[$x;$y;$z] .= lc
}

CAVEATS & LIMITATIONS

It would be nice if Raku had support for Semilist syntax on Iterables, which would allow this

for @zs.&deepgrep(/<:Lu>/, :k) -> @idx {
    @zs[||@idx] .= lc  # Unsupported syntax
}

For now you will have to manually unpack your indices and index into the array, which means the shape should be uniform (eg. a M×N matrix).

Semilist support for Associatives was recently added for v6.e.PREVIEW, so hopefully Iterables will support this syntax when 6e is released.

LICENSE

The Artistic License 2.0

See LICENSE file in the repository for the full license text.