Author: larry
Date: Fri Sep 14 10:34:57 2007
New Revision: 14462
Modified:
doc/trunk/design/syn/S02.pod
doc/trunk/design/syn/S03.pod
doc/trunk/design/syn/S04.pod
doc/trunk/design/syn/S12.pod
Log:
Expunge references to largely redundant "long dot" concept
Modified: doc/trunk/design/syn/S02.pod
==============================================================================
--- doc/trunk/design/syn/S02.pod (original)
+++ doc/trunk/design/syn/S02.pod Fri Sep 14 10:34:57 2007
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 10 Aug 2004
- Last Modified: 4 Sep 2007
+ Last Modified: 14 Sep 2007
Number: 2
- Version: 117
+ Version: 118
This document summarizes Apocalypse 2, which covers small-scale
lexical items and typological issues. (These Synopses also contain
@@ -214,27 +214,48 @@
=item *
-In addition to the general comment forms above, there is a
-whitespace-only comment form that begins with backslash and ends
-with a single dot, separated by 0 or more characters of whitespace,
-which is equivalent to a single dot:
+Some languages such as C allow you to escape newline characters
+to combine lines. Other languages (such as regexes) allow you to
+backslash a space character for various reasons. Perl 6 generalizes
+this notion to any kind of whitespace. Any contiguous whitespace
+(including comments) may be hidden from the parser by prefixing it
+with C<\>. This is known as the "unspace". An unspace can suppress
+any of several whitespace dependencies in Perl. For example, since
+Perl requires an absence of whitespace between a noun and a postfix
+operator, using unspace lets you line up postfix operators:
%hash\ .{$key}
@array\ .[$ix]
$subref\.($arg)
-This is useful for lining up postfixes. This is known as the "long dot",
-partly because it substitutes for a dot without the need for an extra dot:
+As a special case to support the use above, a backslashed dot where
+a postfix is expected is considered a degenerate form of unspace.
+Note that whitespace is not allowed before that, hence
- $object\ .say();
+ $subref \.($arg)
+
+is a syntax error (two terms in a row). And
+
+ foo \.($arg)
+
+will be parsed as a list operator with an argument:
+
+ foo(\$_.($arg))
-The whitespace in the middle may include any of the comment forms above.
-Because comments always count as whitespace, the C<\.> in
+However, other forms of unspace may usefully be preceded by whitespace.
+(Unary uses of backslash may therefore never be followed by whitespace
+or they would be taken as an unspace.)
- $object\#{ foo }.say
+Other postfix operators may also make use of unspace:
-reduce to a "long dot". Valid ways to
-insert a line break into a sequence of method calls include:
+ $number\ ++;
+ $number\ --;
+ 1+3\ i;
+ $object\ .say();
+ $object\#{ your ad here }.say
+
+Anther normal use of a you-don't-see-this-space is typically to put
+a dotted postfix on the next line:
$object\ # comment
.say
@@ -245,14 +266,9 @@
$object\
.say
-=item *
-
-In fact, any whitespace (including comments) may be hidden from the parser by
-prefixing it with C<\>. It does not have to end with a dot. It's just that
-the normal use of a you-don't-see-this-space is typically to put
-a dotted postfix on the next line. But it also lets you continue
+But unspace is mainly about language extensibility: it lets you continue
the line in any situation where a newline might confuse the parser,
-regardless of the currently installed parser. (Unless, of course,
+regardless of your currently installed parser. (Unless, of course,
you override the unspace rule itself...)
Although we say that the unspace hides the whitespace from the parser,
@@ -280,6 +296,10 @@
...
OUTPUT
+Note that this is one of those cases in which it is fine to have
+whitespace before the unspace. (Note also that the example above
+is not meant to spec how the test suite works. :)
+
=item *
An unspace may contain a comment, but a comment may not contain an unspace.
@@ -335,12 +355,12 @@
.++
$x\ # comment
- # inside long dot
+ # inside unspace
.++
$x\ # comment
- # inside "unspace"
- ++ # (but long dot may be preferred...)
+ # inside unspace
+ ++ # (but without the optional postfix dot)
$x\#『 comment
more comment
@@ -355,7 +375,7 @@
].++
A consequence of the postfix rule is that (except when delimiting a
-quote or terminating a "long dot") a dot with whitespace in front
+quote or terminating an unspace) a dot with whitespace in front
of it is always considered a method call on C<$_> where a term is
expected. If a term is not expected at this point, it is a syntax
error. (Unless, of course, there is an infix operator of that name
@@ -1378,7 +1398,7 @@
&foo($arg1, $arg2);
Whitespace is not allowed before the parens, but there is a
-corresponding C<.()> operator, plus the "long dot" forms that allow
+corresponding C<.()> operator, plus the "unspace" forms that allow
you to insert optional whitespace and comments between the backslash
and the dot:
@@ -1730,7 +1750,7 @@
MyType::<$foo>
MyType.::.{'$foo'} # same thing with dots
- MyType\ .::\ .{'$foo'} # same thing with long dots
+ MyType\ .::\ .{'$foo'} # same thing with unspaces
(Directly subscripting the type with either square brackets or curlies
is reserved for various generic type-theoretic operations. In most other
@@ -2151,7 +2171,7 @@
looks for the brackets. Despite not indicating a true subscript,
the brackets are similarly parsed as postfix operators. As postfixes
the brackets may be separated from their initial C<:foo> with either
-dot or "long dot", but nothing else.
+unspace or dot (or both), but nothgin else.
Regardless of syntax, adverbs used as named arguments generally show
up as optional named parameters to the function in question--even
@@ -2584,7 +2604,7 @@
foo.bar # ILLEGAL -- postfix must use foo().bar
foo .bar # foo($_.bar) -- no postfix starts with whitespace
- foo\ .bar # ILLEGAL -- long dot must use foo()\ .bar
+ foo\ .bar # ILLEGAL -- must use foo()\ .bar
foo++ # ILLEGAL -- postfix must use foo()++
foo 1,2,3 # foo(1,2,3) -- args always expected after listop
foo + 1 # foo(+1) -- term always expected after listop
@@ -2654,7 +2674,7 @@
You can also use the :key($value) form to quote the keys of option
pairs. To align values of option pairs, you may use the
-"long dot" postfix forms:
+"unspace" postfix forms:
:longkey\ .($value)
:shortkey\ .<string>
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Fri Sep 14 10:34:57 2007
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 8 Mar 2004
- Last Modified: 13 Sep 2007
+ Last Modified: 14 Sep 2007
Number: 3
- Version: 122
+ Version: 123
=head1 Overview
@@ -343,7 +343,7 @@
As with all postfix operators in Perl 6, no space is allowed between
a term and its postfix. See S02 for why, and for how to work around the
-restriction with a "long dot".
+restriction with an "unspace".
As mutating methods, all these operators dispatch to the type of
the operand and return a result of the same type, but they are legal
@@ -3093,7 +3093,7 @@
@positions.»++; # Same thing, dot form
@positions».++; # Same thing, dot form
@positions.».++; # Same thing, dot form
- @positions\ .»\ .++; # Same thing, long dot form
+ @positions\ .»\ .++; # Same thing, unspace form
@objects.».run();
("f","oo","bar").>>.chars; # (1,2,3)
@@ -3810,7 +3810,7 @@
while $i < 10 { $i++ }
It is, however, still possible to align subscripts and other postfix
-operators by explicitly using the I<long dot> syntax (see S02):
+operators by explicitly using the I<unspace> syntax (see S02):
%monsters.{'cookie'} = Monster.new;
%beatles\.{'ringo'} = Beatle.new;
Modified: doc/trunk/design/syn/S04.pod
==============================================================================
--- doc/trunk/design/syn/S04.pod (original)
+++ doc/trunk/design/syn/S04.pod Fri Sep 14 10:34:57 2007
@@ -1083,7 +1083,7 @@
if $term{$x} # subscript because postfix expected
if $term {$x} # expression followed by statement block
if $term.{$x} # valid subscript with dot
- if $term\ .{$x} # valid subscript with "long dot"
+ if $term\ .{$x} # valid subscript with "unspace"
Similar rules apply to array subscripts:
@@ -1091,7 +1091,7 @@
if $term[$x] # subscript because postfix expected
if $term [$x] # syntax error (two terms in a row)
if $term.[$x] # valid subscript with dot
- if $term\ .[$x] # valid subscript with "long dot"
+ if $term\ .[$x] # valid subscript with "unspace"
And to the parentheses delimiting function arguments:
@@ -1099,7 +1099,7 @@
if $term($x) # function call because operator expected
if $term ($x) # syntax error (two terms in a row)
if $term.($x) # valid function call with dot
- if $term\ .($x) # valid function call with "long dot"
+ if $term\ .($x) # valid function call with "unspace"
Outside of any kind of expression brackets, a final closing curly
on a line (not counting whitespace or comments) always reverts
Modified: doc/trunk/design/syn/S12.pod
==============================================================================
--- doc/trunk/design/syn/S12.pod (original)
+++ doc/trunk/design/syn/S12.pod Fri Sep 14 10:34:57 2007
@@ -344,7 +344,7 @@
.doit() # okay, no arguments
.doit () # ILLEGAL (two terms in a row)
.doit.() # okay, no arguments, same as .doit()
- .doit\ .() # okay, no arguments, same as .doit() (long dot form)
+ .doit\ .() # okay, no arguments, same as .doit() (unspace form)
However, you can turn any of the legal forms above into a list
operator by appending a colon:
