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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.