Author: lwall
Date: 2010-03-03 18:34:04 +0100 (Wed, 03 Mar 2010)
New Revision: 29931
Modified:
docs/Perl6/Spec/S02-bits.pod
Log:
[S02] remove 1/2 and +2-3i literal forms, now rely on angle dwimmery for
literals,
or constant folding otherwise.
Modified: docs/Perl6/Spec/S02-bits.pod
===================================================================
--- docs/Perl6/Spec/S02-bits.pod 2010-03-03 14:16:22 UTC (rev 29930)
+++ docs/Perl6/Spec/S02-bits.pod 2010-03-03 17:34:04 UTC (rev 29931)
@@ -13,8 +13,8 @@
Created: 10 Aug 2004
- Last Modified: 27 Feb 2010
- Version: 206
+ Last Modified: 3 Mar 2010
+ Version: 207
This document summarizes Apocalypse 2, which covers small-scale
lexical items and typological issues. (These Synopses also contain
@@ -133,7 +133,7 @@
=item *
-Except within a string literal, a C<#> character always introduces a comment in
+Except within a quote literal, a C<#> character always introduces a comment in
Perl 6. There are two forms of comment based on C<#>. Embedded
comments require the C<#> to be followed by a backtick (C<`>) plus one
or more opening bracketing characters.
@@ -3013,25 +3013,27 @@
=item *
Rational literals are indicated by separating two integer literals
-(in any radix) with a slash. Whitespace is not allowed on either
-side of the slash:
+(in any radix) with a slash, and enclosing the whole in angles:
- 1/2 # one half literal Rat
- 1 / 2 # 1 divided by 2 (also produces a Rat by constant folding)
+ <1/2> # one half literal Rat
-Note that this essentially overrides precedence to produce a term, so:
+Whitespace is not allowed on either side of the slash or it will
+be split under normal quote-words semantics:
- 1/2 * 3/4
+ < 1 / 2 > # ('1', '/', '2')
+ < 1/2 > # okay, same as <1/2>
-means
+Because of constant folding, you may often get away with leaving
+out the angles:
- (1 / 2) * (3 / 4)
+ 1/2 # 1 divided by 2
-rather than
+However, in that case you have to pay attention to precedence and
associativity.
+The following does I<not> cube C<2/3>:
- ((1 / 2) * 3) / 4
+ 2/3**3 # 2/(3**3), not (2/3)**3
-Decimal fractions not using "e" notation are also stored as C<Rat> values:
+Decimal fractions not using "e" notation are also treated as literal C<Rat>
values:
6.02e23.WHAT # Num
1.23456.WHAT # Rat
@@ -3040,15 +3042,19 @@
=item *
Complex literals are similarly indicated by writing an addition or subtraction
of
-two real numbers without spaces:
+two real numbers (again, without spaces around the operators) inside angles:
- 5.2+1e42i
- 3-1i
+ <5.2+1e42i>
+ < -3-1i >
As with rational literals, constant folding would produce the same
complex number, but this form parses as a single term, ignoring
surrounding precedence.
+(Note that these are not actually special syntactic forms: both
+rational and complex literal forms fall out naturally from the semantic
+rules of qw quotes described below.)
+
=item *
Characters indexed by hex numbers can be interpolated into strings
@@ -3143,11 +3149,13 @@
The purpose of this would be to facilitate compile-time analysis of
multi-method dispatch, when the user prefers angle notation as the
most readable way to represent a list of numbers, which it often is.
+The form with a single value serves as the literal form of numbers
+such as C<Rat> and C<Complex> that would otherwise have to be constructed.
It also gives us a reasonable way of visually isolating any known
literal format as a single syntactic unit:
<-1+2i>.polar
- (-1+2i).polar # same, but less clearly a literal
+ (-1+2i).polar # same, but only by constant folding
The degenerate case C<< <> >> is disallowed as a probable attempt to
do IO in the style of Perl 5; that is now written C<lines()>. (C<<
