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P5chomp zef:lizmat last updated on 2021-09-09

lib/P5chomp.rakumod
use v6.d;

unit module P5chomp:ver<0.0.9>:auth<zef:lizmat>;

proto sub chomp(|) is export {*}
multi sub chomp() { chomp CALLERS::<$_>     }
multi sub chomp(*@a is raw) { chomp(@a) }
multi sub chomp(%h) { chomp(%h.values) }
multi sub chomp(@a) {
    my $chars = 0;
    $chars += chomp($_) for @a;
    $chars
}
multi sub chomp(\s) {
    my $chars = s.chars;
    s .= chomp;
    $chars - s.chars
}

proto sub chop(|) is export {*}
multi sub chop() { chop CALLERS::<$_>     }
multi sub chop(*@a is raw) { chop(@a) }
multi sub chop(%h) { chop(%h.values) }
multi sub chop(@a) {
    if @a {
        my $char = @a[*-1].substr(*-1);
        $_ .= chop for @a;
        $char
    }
    else {
        Nil
    }
}
multi sub chop(\s) {
    my $char = s.substr(*-1);
    s .= chop;
    $char
}

=begin pod

=head1 NAME

Raku port of Perl's chomp() / chop() built-ins

=head1 SYNOPSIS

  use P5chomp; # exports chomp() and chop()

  chomp $a;
  chomp @a;
  chomp %h;
  chomp($a,$b);
  chomp();   # bare chomp may be compilation error to prevent P5isms in Raku

  chop $a;
  chop @a;
  chop %h;
  chop($a,$b);
  chop();      # bare chop may be compilation error to prevent P5isms in Raku

=head1 DESCRIPTION

This module tries to mimic the behaviour of the Perl's C<chomp> and C<chop>
built-ins in Raku as closely as possible.

=head1 ORIGINAL PERL 5 DOCUMENTATION

    chop VARIABLE
    chop( LIST )
    chop    Chops off the last character of a string and returns the character
            chopped. It is much more efficient than "s/.$//s" because it
            neither scans nor copies the string. If VARIABLE is omitted, chops
            $_. If VARIABLE is a hash, it chops the hash's values, but not its
            keys, resetting the "each" iterator in the process.

            You can actually chop anything that's an lvalue, including an
            assignment.

            If you chop a list, each element is chopped. Only the value of the
            last "chop" is returned.

            Note that "chop" returns the last character. To return all but the
            last character, use "substr($string, 0, -1)".

    chomp VARIABLE
    chomp( LIST )
    chomp   This safer version of "chop" removes any trailing string that
            corresponds to the current value of $/ (also known as
            $INPUT_RECORD_SEPARATOR in the "English" module). It returns the
            total number of characters removed from all its arguments. It's
            often used to remove the newline from the end of an input record
            when you're worried that the final record may be missing its
            newline. When in paragraph mode ("$/ = """), it removes all
            trailing newlines from the string. When in slurp mode ("$/ =
            undef") or fixed-length record mode ($/ is a reference to an
            integer or the like; see perlvar) chomp() won't remove anything.
            If VARIABLE is omitted, it chomps $_. Example:

                while (<>) {
                    chomp;  # avoid \n on last field
                    @array = split(/:/);
                    # ...
                }

            If VARIABLE is a hash, it chomps the hash's values, but not its
            keys, resetting the "each" iterator in the process.

            You can actually chomp anything that's an lvalue, including an
            assignment:

                chomp($cwd = `pwd`);
                chomp($answer = <STDIN>);

            If you chomp a list, each element is chomped, and the total number
            of characters removed is returned.

            Note that parentheses are necessary when you're chomping anything
            that is not a simple variable. This is because "chomp $cwd =
            `pwd`;" is interpreted as "(chomp $cwd) = `pwd`;", rather than as
            "chomp( $cwd = `pwd` )" which you might expect. Similarly, "chomp
            $a, $b" is interpreted as "chomp($a), $b" rather than as
            "chomp($a, $b)".

=head1 PORTING CAVEATS

In future language versions of Raku, it will become impossible to access the
C<$_> variable of the caller's scope, because it will not have been marked as
a dynamic variable.  So please consider changing:

    chomp;

to either:

    chomp($_);

or, using the subroutine as a method syntax, with the prefix C<.> shortcut
to use that scope's C<$_> as the invocant:

    .&chomp;

=head1 AUTHOR

Elizabeth Mattijsen <[email protected]>

Source can be located at: https://github.com/lizmat/P5chomp . Comments and
Pull Requests are welcome.

=head1 COPYRIGHT AND LICENSE

Copyright 2018, 2019, 2020, 2021 Elizabeth Mattijsen

Re-imagined from Perl as part of the CPAN Butterfly Plan.

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.

=end pod

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