NAME
List::Gather - Construct lists procedurally without temporary variables
VERSION
version 0.14
SYNOPSIS
use
List::Gather;
my
@list
= gather {
while
(<
$fh
>) {
next
if
/^\s*$/;
next
if
/^\s*
#/;
last
if
/^(?:__END__|__DATA__)$/;
take
$_
if
some_predicate(
$_
);
}
take
@defaults
unless
gathered;
};
DESCRIPTION
This module provides a gather
keyword that allows lists to be constructed procedurally, without the need for a temporary variable.
Within the block controlled by a gather
any call to take
pushes that call's argument list to an implicitly created array.
gather
returns the list of values taken during its block's execution.
FUNCTIONS
gather
gather { ... }
gather({ ... })
gather STMT
Executes the block it has been provided with, collecting all arguments passed to take
calls within it. After execution, the list of values collected is returned.
Note that block gather
executes is equivalent to a do BLOCK
. It is neither a code nor a loop. Loop control keywords, such as next
and last
, as well as return
will behave accordingly.
Parens around the gather
block are optional.
take
take LIST
Collects a LIST
of values within the gather
block it has been compiled in.
take
returns all its arguments.
take
calls outside of the lexical scope of a gather
block are compile time errors. Calling take
is only legal within the dynamic scope its associated gather
block.
gathered
gathered
Returns the list of items collected so far during the execution of a gather
block.
gathered
calls outside of the lexical scope of a gather
block are compile time errors. Calling gathered
outside of the dynamic scope of its associated gather
block is legal.
EXAMPLES
my
@interesting_child_nodes
= gather
for
my
$n
(
@nodes
) {
take
$n
->all_children
if
$n
->is_interesting;
};
my
@last_10_events
= gather {
while
(
$log
->has_event) {
take
$log
->next_event;
}
shift
gathered
while
gathered > 10;
};
my
@search_results
= gather {
$user_interface
->register_status_callback(
sub
{
sprintf
"Searching... Found %d matches so far"
,
scalar
gathered;
});
wait_for_search_results(
sub
{
my
(
$result
) =
@_
;
take
$result
;
},
@search_terms
);
$user_interface
->register_status_callback(
sub
{
sprintf
"Found a total of %d"
,
scalar
gathered;
});
};
my
@leaf_nodes
= gather {
$graph
->visit_all_nodes_recursively(
sub
{
my
(
$node
) =
@_
;
take
$node
if
$node
->is_leaf;
});
};
SEE ALSO
- Syntax::Keyword::Gather
-
A non-lexical gather/take implementation that's otherwise very similar to this one
- Perl6::GatherTake
-
An experimental implementation of a lazily evaluating gather/take
- Perl6::Take
-
A very simple gather/take implementation without lexical scoping
- Perl6::Gather
-
Like Syntax::Keyword::Gather, but reliant on Perl6::Export
- List::Gen
-
A comprehensive suit list generation functions featuring a non-lexical gather/take
ACKNOWLEDGEMENTS
Andrew Main (Zefram) <zefram@fysh.org>
for providing his input in both the design and implementation of this module, and writing much of the infrastructure that made this module possible in the first place
Arthur Axel "fREW" Schmidt <frioux+cpan@gmail.com>
for his input on various aspects of this module as well as the many tests of his Syntax::Keyword::Gather module that this module shamelessly stole
Dave (autarch) Rolsky <autarch@urth.org> and Jesse (doy) Luehrs <doy@tozt.net>
for helping to improve both documentation and test coverage
SUPPORT
Bugs may be submitted through the RT bug tracker (or bug-List-Gather@rt.cpan.org).
AUTHOR
Florian Ragwitz <rafl@debian.org>
CONTRIBUTORS
Karen Etheridge <ether@cpan.org>
Father Chrysostomos <sprout@cpan.org>
David Mitchell <davem@iabyn.com>
Tony Cook <tonyc@cpan.org>
bay-max1 <34803732+bay-max1@users.noreply.github.com>
COPYRIGHT AND LICENCE
This software is copyright (c) 2012 by Florian Ragwitz.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.