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Document [&func] form of infix

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1 parent 7b1a298 commit 10d772fdfd18869a2b454bc7476c739d9dd32c34 @TimToady TimToady committed Jun 27, 2012
Showing with 26 additions and 2 deletions.
  1. +26 −2 S03-operators.pod
@@ -14,8 +14,8 @@ Synopsis 3: Perl 6 Operators
Created: 8 Mar 2004
- Last Modified: 16 June 2012
- Version: 253
+ Last Modified: 27 June 2012
+ Version: 254
=head1 Overview
@@ -4864,6 +4864,8 @@ reader, even if not to the compiler:
@a >>>>> $b # huh?
@a >>[>]>> $b # oh yeah
+=head2 Turning an infix operator into a noun
Any infix function may be referred to as a noun either by the normal long
form or a short form using square brackets directly after the C<&> sigil:
@@ -4883,6 +4885,28 @@ usually be constructed by applying an operator to C<*>:
sort -*, @list # sort reversed numerically
+=head2 Turning a binary function into an infix
+By using the noun form of a binary function inside square brackets,
+it is possible to turn any function that accepts at least two arguments
+into an infix operator. For instance:
+ $y [&atan2] $x # same as atan2($y, $x)
+By itself this may seem relatively useless, but note that it allows
+composition of normal 2-arg functions with all the infix metaoperators.
+Since it is primarily intended for composition with metaoperators,
+this form always assumes a binary function, even if the function could
+accept more arguments; functions that accept more than 2 arguments do
+not thereby accept multiple arguments on the right side. You must use
+the normal functional form to pass three or more positional arguments.
+This form of operator is parsed with a precedence of addition.
+A C<$> is acceptable in place of C<&>, but in either case the
+next character must be either alphabetic or a left parenthesis.
+Otherwise a normal infix operator starting with that character will
+be assumed. Hence C<[&&]> parses as a form of the C<&&> operator.
=head1 Declarators
The list of variable declarators has expanded from C<my> and C<our>

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