NAME¶
Sub::Infix - create a fake infix operator
SYNOPSIS¶
use Sub::Infix;
# Operator needs to be defined (or imported) at compile time.
BEGIN { *plus = infix { $_[0] + $_[1] } };
my $five = 2 |plus| 3;
DESCRIPTION¶
Sub::Infix creates fake infix operators using overloading. It doesn't use source
filters, or Devel::Declare, or any of that magic. (Though Devel::Declare isn't
magic enough to define infix operators anyway; I know; I've tried.) It's pure
Perl, has no non-core dependencies, and runs on Perl 5.6.
The price you pay for its simplicity is that you cannot define an operator that
can be used like this:
my $five = 2 plus 3;
Instead, the operator needs to be wrapped with real Perl operators in one of
three ways:
my $five = 2 |plus| 3;
my $five = 2 /plus/ 3;
my $five = 2 <<plus>> 3;
The advantage of this is that it gives you three different levels of operator
precedence.
You can also call the function a slightly less weird way:
my $five = plus->(2, 3);
How does it work?¶
"2 |plus| 3" is parsed by perl as: "2 | ( &plus() | 3
)".
"&plus()" returns an object that overloads the "|"
operator; let's call that $obj.
The overloaded "$obj | 3" operation stashes 3 inside $obj noting that
the number is the right operand, and returns $obj.
Then "2 | $obj" is evaluated, stashing 2 inside $obj as the left
operand. At this point, the object notices that it has both operands, and
calls the coderef from the definition of the operator, passing it both
operands.
BUGS¶
Please report any bugs to
<
http://rt.cpan.org/Dist/Display.html?Queue=Sub-Infix>.
SEE ALSO¶
<
http://code.activestate.com/recipes/384122-infix-operators/>.
AUTHOR¶
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE¶
This software is copyright (c) 2013-2014 by Toby Inkster.
This is free software; you can redistribute it and/or modify it under the same
terms as the Perl 5 programming language system itself.
DISCLAIMER OF WARRANTIES¶
THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.