Author: larry
Date: Thu May 11 13:33:29 2006
New Revision: 9202
Modified:
doc/trunk/design/syn/S03.pod
Log:
Various clarifications from jerry++ and others
Extra dot is now allowed before hyper postfix since whitespace disallowed there
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Thu May 11 13:33:29 2006
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 8 Mar 2004
- Last Modified: 9 May 2006
+ Last Modified: 11 May 2006
Number: 3
- Version: 27
+ Version: 28
=head1 Changes to existing operators
@@ -28,6 +28,10 @@
=item * The string concatenation C<.> becomes C<~>. Think of it as
"stitching" the two ends of its arguments together.
+=item * All postfix operators that do not start with a dot also have
+an alternate form that does. (The converse does not hold--just because
+you can write C<x().foo> doesn't mean you can write C<x()foo>.)
+
=item * Unary C<~> now imposes a string (C<Str>) context on its argument, and
C<+> imposes a numeric (C<Num>) context (as opposed to being a no-op in Perl
5). Along the same lines, C<?> imposes a boolean (C<Bool>) context, and C<*>
@@ -300,7 +304,10 @@
"list operations", which operate on each element of two lists (or
arrays) and return a list (or array) of the results. Spaces are not
allowed on the "pointy" end of each "hyper", but are allowed on the
-blunt end. For example:
+blunt end (except for postfix operators, which must still follow postfix
+spacing rules, but do for allow an additional dot before the "hyper").
+
+For example:
(1,1,2,3,5) »+« (1,2,3,5,8); # (2,3,5,8,13)
@@ -312,10 +319,15 @@
@negatives = -« @positives;
- @positions »++; # Increment all positions
+ @positions»++; # Increment all positions
- @objects ».run();
- ("f","oo","bar")».chars; # (1,2,3)
+ @positions.»++; # Same thing, dot form
+ @positions».++; # Same thing, dot form
+ @positions.».++; # Same thing, dot form
+ @positions\ .»\ .++; # Same thing, long dot form
+
+ @objects.».run();
+ ("f","oo","bar").>>.chars; # (1,2,3)
Note that method calls are really postfix operators, not infix, so you
shouldn't put a C<«> after the dot.
@@ -344,6 +356,9 @@
my @a = (5,6);
[*] @a; # 5 * 6 = 30
+As with the all metaoperators, space is not allowed inside. The whole
+thing parses as a single token.
+
A reduction operator really is a list operator, and is invoked as one.
Hence, you maybe implement a reduction operator in one of two ways. Either
you can write an explicit list operator:
@@ -403,8 +418,8 @@
However, the zero argument case must of necessity be handled by the
proto version, since there is no type information to dispatch on.
Operators that wish to specify an identity value should do so by
-specifying the proto listop. Among the builtin operators, [+]()
-returns 0 and [*]() returns 1, for instance.
+specifying the proto listop. Among the builtin operators, C<[+]()>
+returns 0 and C<[*]()> returns 1, for instance.
By default, if there is one argument, the built-in reduce operators
return that one argument. However, this default doesn't make sense
@@ -876,7 +891,7 @@
Perl 6 has 22 precedence levels (which is fewer than Perl 5):
terms 42 "eek" $x /abc/ (1+2) a(1) :by(2) .meth listop
- method postfix . .+ .? .* .() .[] .{} .«» .=
+ method postfix . .+ .? .* .() .[] .{} .:: .«» .=
autoincrement ++ --
exponentiation **
symbolic unary ! + - ~ ? $ @ % & * ** +^ ~^ ?^ \ ^ =
@@ -890,7 +905,7 @@
tight and &&
tight or || ^^ //
ternary ?? !!
- assignment = := ::= += -= **= xx= etc. (and also =>)
+ assignment = := ::= += -= **= xx= .= etc. (and also =>)
list item separator , ¥
list op (rightward) <== print push any all true not etc. and ()= rightward
pipe forward ==>
