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 liz@raku.rocks

If you like this module, or what I’m doing more generally, committing to a small sponsorship would mean a great deal to me!

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

COPYRIGHT AND LICENSE

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.