/ 
Ekorn-Pipeline-v0.1.2
/ Ekorn::Pipeline::Stages::Flow

NAME

Ekorn::Pipeline::Stages::Flow - stages taking or dropping values: take, drop, take_while and drop_while

SYNOPSIS

use Ekorn::Pipeline;
use Ekorn::Pipeline::Stages::Flow;    # take and drop

# The third page of ten
my @page = Ekorn::Pipeline->new(drop(20), take(10))->(@names);

use Ekorn::Pipeline::Stages::Flow qw(:DEFAULT take_while drop_while);

# A mail's headers: its lines up to the first blank one
my $headers = Ekorn::Pipeline->new(take_while { m( \S )x })
    ->iterator(sub { scalar(<$fh>) // () });

DESCRIPTION

Stages that decide which values go on, by their place or by a test, whatever the values are. Each function returns a stage, and checks what it's given when it's called, not on each value. Those that keep state, take, drop and drop_while, are made with Ekorn::Pipeline::Gather, so they start afresh on each run: each call of a pipeline with values, and each iterator made from it.

take and take_while end the pipeline with Ekorn::Pipeline::Stop once they have passed on all they will, so an iterator calls its source no more.

FUNCTIONS

take and drop are exported by default; take_while and drop_while on request, or all four with :all. To have the defaults and one more, name :DEFAULT too:

use Ekorn::Pipeline::Stages::Flow qw(:DEFAULT take_while);

take

take($count)

Passes on the first $count values, then stops the pipeline. With fewer values, passes them all on. take(0) passes on none, but still sees the first value, as a stage isn't called until there is one.

drop

drop($count)

Drops the first $count values, and passes on the rest. With take, it gives a page:

drop(20), take(10)    # the 21st to the 30th

take_while

take_while { ... }

Passes on values while the block is true of them, given each in $_ and as its argument, then stops the pipeline at the first it's false of, which isn't passed on.

drop_while

drop_while { ... }

Drops values while the block is true of them, given each in $_ and as its argument, and passes on the rest, from the first it's false of. Once it's false, the block isn't called again on that run.

DIAGNOSTICS

Expected a count of 0 or more

take or drop was given something other than a whole number.

Expected a code reference

take_while or drop_while was given something other than a block or code reference.

SEE ALSO

Ekorn::Pipeline, Ekorn::Pipeline::Gather, Ekorn::Pipeline::Stop

AUTHOR

Iain Campbell <cpanic@cpan.org>

LICENSE

Copyright (c) 2024-2026 by Iain Campbell.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.