NAME

Raku port of Perl's print() and associated built-ins

SYNOPSIS

use P5print; # exports print, printf, say, STDIN, STDOUT, STDERR

print STDOUT, "foo";

printf STDERR, "%s", $bar;

say STDERR, "foobar";      # same as "note"

DESCRIPTION

This module tries to mimic the behaviour of Perl's print, printf and say built-ins as closely as possible in the Raku Programming Language.

ORIGINAL PERL 5 DOCUMENTATION

print FILEHANDLE LIST
    print FILEHANDLE
    print LIST
    print   Prints a string or a list of strings. Returns true if successful.
            FILEHANDLE may be a scalar variable containing the name of or a
            reference to the filehandle, thus introducing one level of
            indirection. (NOTE: If FILEHANDLE is a variable and the next token
            is a term, it may be misinterpreted as an operator unless you
            interpose a "+" or put parentheses around the arguments.) If
            FILEHANDLE is omitted, prints to the last selected (see "select")
            output handle. If LIST is omitted, prints $_ to the currently
            selected output handle. To use FILEHANDLE alone to print the
            content of $_ to it, you must use a real filehandle like "FH", not
            an indirect one like $fh. To set the default output handle to
            something other than STDOUT, use the select operation.

The current value of $, (if any) is printed between each LIST
            item. The current value of $\ (if any) is printed after the entire
            LIST has been printed. Because print takes a LIST, anything in the
            LIST is evaluated in list context, including any subroutines whose
            return lists you pass to "print". Be careful not to follow the
            print keyword with a left parenthesis unless you want the
            corresponding right parenthesis to terminate the arguments to the
            print; put parentheses around all arguments (or interpose a "+",
            but that doesn't look as good).

If you're storing handles in an array or hash, or in general
            whenever you're using any expression more complex than a bareword
            handle or a plain, unsubscripted scalar variable to retrieve it,
            you will have to use a block returning the filehandle value
            instead, in which case the LIST may not be omitted:

print { $files[$i] } "stuff\n";
                print { $OK ? STDOUT : STDERR } "stuff\n";

Printing to a closed pipe or socket will generate a SIGPIPE
            signal. See perlipc for more on signal handling.

printf FILEHANDLE FORMAT, LIST
    printf FILEHANDLE
    printf FORMAT, LIST
    printf  Equivalent to "print FILEHANDLE sprintf(FORMAT, LIST)", except
            that $\ (the output record separator) is not appended. The FORMAT
            and the LIST are actually parsed as a single list. The first
            argument of the list will be interpreted as the "printf" format.
            This means that "printf(@_)" will use $_[0] as the format. See
            sprintf for an explanation of the format argument. If "use locale"
            (including "use locale ':not_characters'") is in effect and
            POSIX::setlocale() has been called, the character used for the
            decimal separator in formatted floating-point numbers is affected
            by the LC_NUMERIC locale setting. See perllocale and POSIX.

For historical reasons, if you omit the list, $_ is used as the
            format; to use FILEHANDLE without a list, you must use a real
            filehandle like "FH", not an indirect one like $fh. However, this
            will rarely do what you want; if $_ contains formatting codes,
            they will be replaced with the empty string and a warning will be
            emitted if warnings are enabled. Just use "print" if you want to
            print the contents of $_.

Don't fall into the trap of using a "printf" when a simple "print"
            would do. The "print" is more efficient and less error prone.

say FILEHANDLE LIST
    say FILEHANDLE
    say LIST
    say     Just like "print", but implicitly appends a newline. "say LIST" is
            simply an abbreviation for "{ local $\ = "\n"; print LIST }". To
            use FILEHANDLE without a LIST to print the contents of $_ to it,
            you must use a real filehandle like "FH", not an indirect one like
            $fh.

This keyword is available only when the "say" feature is enabled,
            or when prefixed with "CORE::"; see feature. Alternately, include
            a "use v5.10" or later to the current scope.

PORTING CAVEATS

Syntax differences

In Raku, there must be a comma after the handle, as opposed to Perl where the whitespace after the handle indicates indirect object syntax.

print STDERR "whee!";   # Perl way

print STDERR, "whee!";  # Raku mimicing Perl

Parentheses

Because of some overzealous checks for Perl 5isms, it is necessary to put parentheses when using print and say as a function. Since the 2018.09 Rakudo compiler release, it is possible to use the isms pragma to avoid having to do that:

use isms <Perl5>;
    $_ = "foo";
    say;    # foo

$_ no longer accessible from caller's scope

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

print;

to either:

print($_);

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

.&print;

IDIOMATIC PERL 6 WAYS

When needing to write to specific handle, it's probably easier to use the method form.

$handle.print("foo");
    $handle.printf("foo");
    $handle.say("foo");

If you want to do a say on STDERR, this is easier done with the note builtin function:

$*ERR.say("foo");  # "foo\n" on standard error
    note "foo";        # same

AUTHOR

Elizabeth Mattijsen <[email protected]>

Source can be located at: https://github.com/lizmat/P5print . Comments and Pull Requests are welcome.

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.