Author: larry
Date: Fri Jun 15 12:10:26 2007
New Revision: 14422
Modified:
doc/trunk/design/syn/S03.pod
doc/trunk/design/syn/S12.pod
Log:
some cleanup suggestions by dduncan++
spec out several migration error catching policies, like infix:<?> pseudo-op
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Fri Jun 15 12:10:26 2007
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 8 Mar 2004
- Last Modified: 2 Jun 2007
+ Last Modified: 15 Jun 2007
Number: 3
- Version: 116
+ Version: 117
=head1 Overview
@@ -220,6 +220,10 @@
.meth # call on $_
.=meth # modify $_
+Note that this may occur only where a term is expected. Where a
+postfix is expected, it is a postfix. If only an infix is expected
+(that is, after a term with intervening whitespace), it is a syntax error.
+
=item *
Listop (leftward)
@@ -312,6 +316,16 @@
$x.:<++> # prefix:<++>($x)
+=item *
+
+There is specifically no C<< infix:<.> >> operator, so
+
+ $foo . $bar
+
+will always result in a compile-time error indicating the user should
+use C<< infix:<~> >> instead. This is to catch an error likely to
+be made by Perl 5 programmers learning Perl 6.
+
=back
=head2 Autoincrement precedence
@@ -377,14 +391,14 @@
=item *
-Autoincrement prefix:<++> or postfix:<++> operator
+Autoincrement C<< prefix:<++> >> or C<< postfix:<++> >> operator
$x++
++$x;
=item *
-Autodecrement prefix:<--> or postfix:<--> operator
+Autodecrement C<< prefix:<--> >> or C<< postfix:<--> >> operator
$x--
--$x
@@ -397,7 +411,7 @@
=item *
-infix:<**> exponentiation operator
+C<< infix:<**> >> exponentiation operator
$x ** 2
@@ -418,7 +432,7 @@
=item *
-prefix:<?>, boolean context
+C<< prefix:<?> >>, boolean context
?$x
@@ -428,7 +442,7 @@
=item *
-prefix:<!>, boolean negation
+C<< prefix:<!> >>, boolean negation
!$x
@@ -437,7 +451,7 @@
=item *
-prefix:<+>, numeric context
+C<< prefix:<+> >>, numeric context
+$x
@@ -450,7 +464,7 @@
=item *
-prefix:<->, numeric negation
+C<< prefix:<-> >>, numeric negation
-$x
@@ -458,7 +472,7 @@
=item *
-prefix:<~>, string context
+C<< prefix:<~> >>, string context
~$x
@@ -467,7 +481,7 @@
=item *
-prefix:<|>, flatten object into arglist
+C<< prefix:<|> >>, flatten object into arglist
| $capture
@@ -476,7 +490,7 @@
=item *
-prefix:<+^>, numeric bitwise negation
+C<< prefix:<+^> >>, numeric bitwise negation
+^$x
@@ -484,14 +498,14 @@
=item *
-prefix:<~^>, string bitwise negation
+C<< prefix:<~^> >>, string bitwise negation
~^$x
Coerces to string buffer and then does bitwise negation on each element.
=item *
-prefix:<?^>, boolean bitwise negation
+C<< prefix:<?^> >>, boolean bitwise negation
?^$x
@@ -499,7 +513,7 @@
=item *
-prefix:<\>, Capture constructor
+C<< prefix:<\> >>, Capture constructor
\$x
[EMAIL PROTECTED]
@@ -511,7 +525,7 @@
=item *
-prefix:<^>, upto operator
+C<< prefix:<^> >>, upto operator
^$limit
@@ -520,7 +534,7 @@
=item *
-prefix:<=>, iterate iterator
+C<< prefix:<=> >>, iterate iterator
=$iterator
@@ -543,7 +557,7 @@
=item *
-infix:<*>
+C<< infix:<*> >>
$x*$y
@@ -551,7 +565,7 @@
=item *
-infix:</>
+C<< infix:</> >>
$numerator / $denominator
@@ -571,7 +585,7 @@
=item *
-infix:<div>, generic division
+C<< infix:<div> >>, generic division
$numerator div $denominator
@@ -589,7 +603,7 @@
=item *
-infix:<%>, modulus
+C<< infix:<%> >>, modulus
$x % $mod
@@ -597,15 +611,15 @@
=item *
-infix:<mod>, generic modulus
+C<< infix:<mod> >>, generic modulus
$x mod $mod
-Dispatches to the infix:<mod> multi most appropriate to the operand types.
+Dispatches to the C<< infix:<mod> >> multi most appropriate to the operand
types.
=item *
-infix:<x>, string/buffer replication
+C<< infix:<x> >>, string/buffer replication
$string x $count
@@ -620,7 +634,7 @@
=item *
-infix:<xx>, list replication
+C<< infix:<xx> >>, list replication
@list xx $count
@@ -637,7 +651,7 @@
=item *
-infix:{'+&'}, numeric bitwise and
+C<< infix:{'+&'} >>, numeric bitwise and
$x +& $y
@@ -645,13 +659,13 @@
=item *
-infix:{'+<'}, numeric shift left
+C<< infix:{'+<'} >>, numeric shift left
$integer +< $bits
=item *
-infix:{'+>'}, numeric shift right
+C<< infix:{'+>'} >>, numeric shift right
$integer +> $bits
@@ -660,19 +674,19 @@
=item *
-infix:<~&>, buffer bitwise and
+C<< infix:<~&> >>, buffer bitwise and
$x ~& $y
=item *
-infix:{'~<'}, buffer bitwise shift left
+C<< infix:{'~<'} >>, buffer bitwise shift left
$buf ~< $bits
=item *
-infix:{'~>'}, buffer bitwise shift right
+C<< infix:{'~>'} >>, buffer bitwise shift right
$buf ~> $bits
@@ -681,7 +695,7 @@
=item *
-infix:<?&>, boolean bitwise and
+C<< infix:<?&> >>, boolean bitwise and
$x ?& $y
@@ -697,55 +711,55 @@
=item *
-infix:<+>, numeric addition
+C<< infix:<+> >>, numeric addition
$x + $y
=item *
-infix:<->, numeric subtraction
+C<< infix:<-> >>, numeric subtraction
$x - $y
=item *
-infix:<~>, string/buffer concatenation
+C<< infix:<~> >>, string/buffer concatenation
$x ~ $y
=item *
-infix:<+|>, numeric bitwise inclusive or
+C<< infix:<+|> >>, numeric bitwise inclusive or
$x +| $y
=item *
-infix:<+^> numeric bitwise exclusive or
+C<< infix:<+^> >> numeric bitwise exclusive or
$x +^ $y
=item *
-infix:<~|>, buffer bitwise inclusive or
+C<< infix:<~|> >>, buffer bitwise inclusive or
$x ~| $y
=item *
-infix:<~^> buffer bitwise exclusive or
+C<< infix:<~^> >> buffer bitwise exclusive or
$x ~^ $y
=item *
-infix:<?|>, boolean bitwise inclusive or
+C<< infix:<?|> >>, boolean bitwise inclusive or
$x ?| $y
=item *
-infix:<?^> boolean bitwise exclusive or
+C<< infix:<?^> >> boolean bitwise exclusive or
$x ?^ $y
@@ -757,7 +771,7 @@
=item *
-infix:<&>, all() operator
+C<< infix:<&> >>, all() operator
$x & $y
@@ -769,13 +783,13 @@
=item *
-infix:<|>, any() operator
+C<< infix:<|> >>, any() operator
$x | $y
=item *
-infix:<^>, one() operator
+C<< infix:<^> >>, one() operator
$x ^ $y
@@ -802,13 +816,13 @@
=item *
-infix:<but>
+C<< infix:<but> >>
$value but Mixin
=item *
-infix:<does>
+C<< infix:<does> >>
$object does Mixin
@@ -866,7 +880,7 @@
=item *
-infix:<==> etc.
+C<< infix:<==> >> etc.
== != < <= > >=
@@ -874,7 +888,7 @@
=item *
-infix:<eq> etc.
+C<< infix:<eq> >> etc.
eq ne lt le gt ge
@@ -956,7 +970,7 @@
=item *
-infix:<&&>, short-circuit and
+C<< infix:<&&> >>, short-circuit and
$condition && $whentrue
@@ -973,7 +987,7 @@
=item *
-infix:<||>, short-circuiting inclusive-or
+C<< infix:<||> >>, short-circuiting inclusive-or
$condition || $whenfalse
@@ -988,7 +1002,7 @@
=item *
-infix:<^^>, exclusive-or
+C<< infix:<^^> >>, exclusive-or
$x ^^ $y
@@ -999,7 +1013,7 @@
=item *
-infix:<//>, defined-or
+C<< infix:<//> >>, defined-or
$value // $default
@@ -1073,6 +1087,14 @@
my $x = hmm() ?? 1 !! 2; # much better
+=item *
+
+C<< infix:<?> >>
+
+To catch likely errors by people familiar with C-derived languages
+(including Perl 5), a bare question mark in infix position will
+produce an error suggesting that the user use C<?? !!> instead.
+
=back
=head2 Item assignment precedence
@@ -1081,7 +1103,7 @@
=item *
-infix:<=>
+C<< infix:<=> >>
$x = 1, $y = 2;
@@ -1090,7 +1112,7 @@
=item *
-infix:<:=>, run-time binding
+C<< infix:<:=> >>, run-time binding
$signature := $capture
@@ -1125,7 +1147,7 @@
=item *
-infix:<::=>, compile-time binding
+C<< infix:<::=> >>, compile-time binding
$signature ::= $capture
@@ -1135,7 +1157,7 @@
=item *
-infix:{'=>'}, Pair constructor
+C<< infix:{'=>'} >>, Pair constructor
foo => 1, bar => "baz"
@@ -1163,13 +1185,13 @@
=item *
-prefix:<true>
+C<< prefix:<true> >>
true any(@args) eq '-v' | '-V'
=item *
-prefix:<not>
+C<< prefix:<not> >>
not any(@args) eq '-v' | '-V'
@@ -1181,7 +1203,7 @@
=item *
-infix:<,>, the argument separator
+C<< infix:<,> >>, the argument separator
1, 2, 3, @many
@@ -1201,13 +1223,13 @@
=item *
-infix:<Z>, the zip operator
+C<< infix:<Z> >>, the zip operator
1,2 Z 3,4 # (1,3),(2,4)
=item *
-infix:<minmax>, the minmax operator
+C<< infix:<minmax> >>, the minmax operator
$min0, $max0 minmax $min1, $max1 # ($min0 min $min1, $max0 max $max1)
@@ -1226,7 +1248,7 @@
=item *
-infix:<X>, the cross operator
+C<< infix:<X> >>, the cross operator
1,2 X 3,4 # (1,3), (1,4), (2,3), (2,4)
@@ -1269,7 +1291,7 @@
=item *
-infix:<=>, list assignment
+C<< infix:<=> >>, list assignment
@array = 1,2,3;
@@ -1291,7 +1313,7 @@
=item *
-infix:<:>, the invocant marker
+C<< infix:<:> >>, the invocant marker
say $*OUT: "howdy, world"
@@ -1435,7 +1457,7 @@
=item *
-infix:<and>, short-circuit and
+C<< infix:<and> >>, short-circuit and
$condition and $whentrue
@@ -1452,7 +1474,7 @@
=item *
-infix:<or>, short-circuit inclusive or
+C<< infix:<or> >>, short-circuit inclusive or
$condition or $whenfalse
@@ -1462,7 +1484,7 @@
=item *
-infix:<xor>, exclusive or
+C<< infix:<xor> >>, exclusive or
$x xor $y
@@ -1473,7 +1495,7 @@
=item *
-infix:<err>, short-circuit defined-or
+C<< infix:<err> >>, short-circuit defined-or
$value err $default
@@ -1579,10 +1601,17 @@
Perl 5's C<${...}>, C<@{...}>, C<%{...}>, etc. dereferencing
forms are now C<$(...)>, C<@(...)>, C<%(...)>, etc. instead.
Listop-like forms use the bare sigil following by whitespace.
+Use of the Perl 5 curly forms will result in an error message
+pointing the user to the new forms.
=item *
-C<< -> >> becomes C<.>, like the rest of the world uses.
+C<< -> >> becomes C<.>, like the rest of the world uses. There is
+a pseudo C<< postfix:{'->'} >> operator that produces a compile-time
+error reminding Perl 5 users to use dot instead. (The "pointy block"
+use of C<< -> >> in Perl 5 requires preceding whitespace when the arrow
+could be confused with a postfix, that is when an infix is expected.
+Preceding whitespace is not required in term position.)
=item *
@@ -1652,6 +1681,10 @@
Note that C<:s> still returns the filesize, but C<:!s> is true
only if the file is of size 0.
+(Inadvertent use of the Perl 5 forms will normally result in treatment
+as a negated postdeclared subroutine, which is likely to produce an
+error message at the end of compilation.)
+
=item *
All postfix operators that do not start with a dot also have
@@ -1717,7 +1750,8 @@
=item *
-The C<? :> conditional operator becomes C<?? !!>.
+The C<? :> conditional operator becomes C<?? !!>. A pseudo operator,
+C<< infix:<?> >>, catches migratory brainos at compile time.
=item *
@@ -1730,6 +1764,9 @@
In item context comma C<,> now constructs a C<List> object from its
operands. You have to use a C<[*-1]> subscript to get the last one.
+(Note the C<*>. Negative subscripts no longer implicitly count from
+the end; in fact, the compiler may complain if you use C<[-1]> on an
+object known at compile time not to have negative subscripts.)
=item *
@@ -3099,6 +3136,8 @@
[^]() # one()
[!==]() # Bool::False (also for 1 arg)
[==]() # Bool::True (also for 1 arg)
+ [before]() # Bool::True (also for 1 arg)
+ [after]() # Bool::True (also for 1 arg)
[<]() # Bool::True (also for 1 arg)
[<=]() # Bool::True (also for 1 arg)
[>]() # Bool::True (also for 1 arg)
Modified: doc/trunk/design/syn/S12.pod
==============================================================================
--- doc/trunk/design/syn/S12.pod (original)
+++ doc/trunk/design/syn/S12.pod Fri Jun 15 12:10:26 2007
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 27 Oct 2004
- Last Modified: 31 May 2007
+ Last Modified: 15 May 2007
Number: 12
- Version: 54
+ Version: 55
=head1 Overview
@@ -225,6 +225,16 @@
$obj."$methodname"(1,2,3) # use contents of $methodname as method name
$obj.'$methodname'(1,2,3) # no interpolation; call method with $ in name!
+[Note: to help catch the mistaken use of C<< infix:<.> >> as a string
+concatenation operator, Perl 6 will warn you about "useless use of
+quotes" at compile time if the string inside quotes is an identifier.
+(It does not warn about non-identifier strings, but such strings are
+likely to produce missing method errors at run time in any case.)
+Also, if there is whitespace around an intended C<.> concatenation,
+it cannot be parsed as a method call at all; instead if fails at
+compile time because standard Perl 6 has no C<< infix:<.> >> operator
+unless the user happens to have defined one (bad idea).]
+
For situations where you already have a method located, you
can use a simple scalar variable in place of method name:
