Re: Synopsis 02: Range objects
HaloO, Jon Lang wrote: '' and '=' numify their arguments before comparing them. 'lt' and 'le' stringify their arguments before comparing them. 'before' compares its arguments without any coercion. Note that there's no equivalent to '='. This last one is !after and !before is '='. Regards, TSa. -- The unavoidable price of reliability is simplicity -- C.A.R. Hoare Simplicity does not precede complexity, but follows it. -- A.J. Perlis 1 + 2 + 3 + 4 + ... = -1/12 -- Srinivasa Ramanujan
Re: Synopsis 02: Range objects
On Mon, Aug 31, 2009 at 12:42 AM, TSa thomas.sandl...@vts-systems.de wrote: HaloO, Jon Lang wrote: '' and '=' numify their arguments before comparing them. 'lt' and 'le' stringify their arguments before comparing them. 'before' compares its arguments without any coercion. Note that there's no equivalent to '='. This last one is !after and !before is '='. Only when total ordering is involved. -- Jonathan Dataweaver Lang
r28146 - docs/Perl6/Spec
Author: lwall Date: 2009-08-31 21:56:55 +0200 (Mon, 31 Aug 2009) New Revision: 28146 Modified: docs/Perl6/Spec/S02-bits.pod Log: [S02] remove fossil noticed by pmichaud++ Modified: docs/Perl6/Spec/S02-bits.pod === --- docs/Perl6/Spec/S02-bits.pod2009-08-31 19:55:44 UTC (rev 28145) +++ docs/Perl6/Spec/S02-bits.pod2009-08-31 19:56:55 UTC (rev 28146) @@ -13,8 +13,8 @@ Created: 10 Aug 2004 -Last Modified: 24 Aug 2009 -Version: 174 +Last Modified: 31 Aug 2009 +Version: 175 This document summarizes Apocalypse 2, which covers small-scale lexical items and typological issues. (These Synopses also contain @@ -633,10 +633,11 @@ is not required to unless we can do so portably and efficiently. CNum must support the largest native floating point format that runs at full speed.) -CRat supports arbitrary precision rational arithmetic. However, -dividing two CInt objects using C infix:/ produces a -fraction of CNum type, not a ratio. You can produce a ratio by -using C infix:div on two integers instead. +CRat supports arbitrary precision rational arithmetic. +Dividing two CInt objects using C infix:/ produces a +a CRat, which is generally usable anywhere a CNum is usable, but +may also be explicitly cast to CNum. (Also, if either side is +CNum already, C infix:/ gives you a CNum instead of a CRat.) Lower-case types like Cint and Cnum imply the native machine representation for integers and floating-point numbers,
Re: r28113 - docs/Perl6/Spec
pugs-comm...@feather.perl6.nl wrote: Author: lwall Date: 2009-08-29 21:06:40 +0200 (Sat, 29 Aug 2009) New Revision: 28113 Modified: docs/Perl6/Spec/S03-operators.pod Log: [S03] some tidying of /, %, div, and mod snip @@ -699,7 +699,16 @@ $numerator / $denominator -If either operand is of CNum type, converts both operands to CNum +Performs division of real or complex numbers, returning a real or complex +number of appropriate type. + +If both operands are of integer type, the operator returns the +corresponding CRat value. snip $numerator div $denominator snip -Use of Cdiv on two CInt values results in a ratio of the CRat type. +Use of Cdiv on built-in integer types is equivalent to taking the +floor of a real division: +$x div $y == floor($x/$y); snippage This is a great move; thanks for this change. So now writing things like 5/43 in code will DWIM and produce a Rat which maintains the intended value exactly, with no floating-point imprecision; and so plain 5/43 is now a plain Rat literal, same as 1.23 is. Similarly its good that by default 'div' can be counted on to result in values of the same type as its operands, such as Int,Int--Int. Generally speaking, the simpler/terse looking numeric operators like / should produce exact results from exact inputs where possible, and leave the inexact (float) results from exact inputs to more complex/verbose looking operators. Much appreciated. -- Darren Duncan
Re: r28113 - docs/Perl6/Spec
On Mon, Aug 31, 2009 at 01:28:08PM -0700, Darren Duncan wrote: This is a great move; thanks for this change. So now writing things like 5/43 in code will DWIM and produce a Rat which maintains the intended value exactly, with no floating-point imprecision; and so plain 5/43 is now a plain Rat literal, same as 1.23 is. FWIW, presently the specification somewhat implies that 1.23 is a Num literal, and doesn't say anything about it producing a Rat. (Yes, conversations on #perl6 have indicated that it may be otherwise, but nothing is currently in the spec about it.) S02:401 : One consequence of all this is that you may no longer write a Num as C42. with just a trailing dot. You must instead say either C42 or C42.0. Pm
Re: r28113 - docs/Perl6/Spec
Patrick R. Michaud wrote: On Mon, Aug 31, 2009 at 01:28:08PM -0700, Darren Duncan wrote: This is a great move; thanks for this change. So now writing things like 5/43 in code will DWIM and produce a Rat which maintains the intended value exactly, with no floating-point imprecision; and so plain 5/43 is now a plain Rat literal, same as 1.23 is. FWIW, presently the specification somewhat implies that 1.23 is a Num literal, and doesn't say anything about it producing a Rat. (Yes, conversations on #perl6 have indicated that it may be otherwise, but nothing is currently in the spec about it.) S02:401 : One consequence of all this is that you may no longer write a Num as C42. with just a trailing dot. You must instead say either C42 or C42.0. My understanding of Perl 6 to date is that: Num is effectively a wrapper type that represents a real number some-how and that internally its representation could either be an Int or a Rat or something that does IEEE floating-point or something else. That is, any Int or Rat could be exactly matched by a Num but a Num could also represent other values that neither an Int nor a Rat can, or that Num can do approximate (eg, IEEE float) math while Int and Rat would only do exact math (and so not support certain ops that might result in an irrational). And so, any context that expects a Num will accept any Int or Rat, but the reverse may not be true without coersion. That is, Num will support both exact and inexact numbers, but Int/Rat don't. Therefore, any literal such as 42.0, because it is exact, should be interpreted as a plain Rat, same as 42 is interpreted as a plain Int, but they would still work with any context wanting a Num. I also don't think this interpretation would harm type-based routine dispatch since using Rat ops on Rat-compatible inputs would still produce results suitable for use in Num contexts, I would think. -- Darren Duncan
r28150 - docs/Perl6/Spec
Author: lwall
Date: 2009-09-01 01:42:06 +0200 (Tue, 01 Sep 2009)
New Revision: 28150
Modified:
docs/Perl6/Spec/S03-operators.pod
Log:
[S03] steal ::= for readonly binding ala sigs
Modified: docs/Perl6/Spec/S03-operators.pod
===
--- docs/Perl6/Spec/S03-operators.pod 2009-08-31 21:06:36 UTC (rev 28149)
+++ docs/Perl6/Spec/S03-operators.pod 2009-08-31 23:42:06 UTC (rev 28150)
@@ -14,8 +14,8 @@
Created: 8 Mar 2004
-Last Modified: 29 Aug 2009
-Version: 170
+Last Modified: 31 Aug 2009
+Version: 171
=head1 Overview
@@ -1465,14 +1465,28 @@
=item *
-C infix:::= , compile-time binding
+C infix:::= , bind and make readonly
$signature ::= $capture
-This does the same as C:= except it does it at compile time. (This implies
-that the expression on the right is also evaluated at compile time; it does
-not bind a lazy thunk.)
+This does the same as C:=, then marks any destination parameters as
+readonly (unless the individual parameter overrides this with either
+the Crw trait or the Ccopy trait). It's particularly useful
+for establishing readonly context variables for a dynamic scope:
+{
+my $*OUT ::= open($file, :w) || die $!;
+doit(); # runs with redirected stdout
+}
+doit(); # runs with original stdout
+
+If Cdoit wants to change C$*OUT, it must declare its own
+contextual variable. It may not simply assign to C$*OUT.
+
+Note that the semantics of C::= are virtually identical to
+the normal binding of arguments to formal subroutine parameters
+(which also default to readonly).
+
=item *
C infix:{'='} , Pair constructor
r28151 - docs/Perl6/Spec
Author: lwall Date: 2009-09-01 02:09:52 +0200 (Tue, 01 Sep 2009) New Revision: 28151 Modified: docs/Perl6/Spec/S02-bits.pod docs/Perl6/Spec/S06-routines.pod Log: [S02,S06] make 'is context' implicit on $*foo variable declarations orthogonalize readonly semantics to rely on ::= initialization Modified: docs/Perl6/Spec/S02-bits.pod === --- docs/Perl6/Spec/S02-bits.pod2009-08-31 23:42:06 UTC (rev 28150) +++ docs/Perl6/Spec/S02-bits.pod2009-09-01 00:09:52 UTC (rev 28151) @@ -14,7 +14,7 @@ Created: 10 Aug 2004 Last Modified: 31 Aug 2009 -Version: 175 +Version: 176 This document summarizes Apocalypse 2, which covers small-scale lexical items and typological issues. (These Synopses also contain @@ -2091,7 +2091,8 @@ user-defined variable from you. In fact, that's the default, and a lexical variable must have the trait Cis context to be visible via CCALLER. (C$_, C$! and C$/ are always -contextual.) If the variable is not visible in the caller, it returns +contextual, as are any variables whose declared names contain a C* twigil.) +If the variable is not visible in the caller, it returns failure. Variables whose names are visible at the point of the call but that come from outside that lexical scope are controlled by the scope in which they were originally declared as contextual. @@ -2100,13 +2101,11 @@ it happens to be declared). Likewise C CALLER::CALLER::$x depends only on the declaration of C$x visible in your caller's caller. -Any lexical declared with the Cis context trait is by default -considered readonly outside the current lexical scope. You may -add a trait argument of C rw to allow called routines to -modify your value. C$_, C$!, and C$/ are C contextrw -by default. In any event, the declaring scope can always access the -variable as if it were an ordinary variable; the restriction on writing -applies only to access via the C* twigil. +User-defined contextual variables should generally be initialized with +C::= unless it is necessary for variable to be modified. (Marking +dynamic variables as readonly is very helpful in terms of sharing +the same value among competing threads, since a readonly variable +need not be locked.) =item * @@ -2128,26 +2127,25 @@ semicolons as appropriate to the current operating system. Usage of the C%*FOO form is currently undefined. -Unlike CCALLER, CCONTEXT will see a contextual variable that is declared in -the current scope, however it will not be writeable via CCONTEXT unless -declared C is contextrw , even if the variable itself is -modifiable in that scope. (If it is, you should just use the bare -variable itself to modify it.) Note that C$*_ will always see -the C$_ in the current scope, not the caller's scope. You may -use C CALLER::$*foo to bypass a contextual definition of C$foo -in your current context, such as to initialize it with the outer -contextual value: +Unlike CCALLER, CCONTEXT will see a contextual variable that is +declared in the current scope, since it starts search 0 scopes up the +stack rather than 1. You may, however, use C CALLER::$*foo +to bypass a contextual definition of C$*foo in your current context, +such as to initialize it with the outer contextual value: -my $foo is context = CALLER::$*foo; +my $*foo ::= CALLER::$*foo; -The Ctemp maybe used on a contextual variable to perform a similar operation: +The Ctemp maybe used without an initializer on a contextual variable +to perform a similar operation: temp $*foo; The main difference is that by default it initializes the new -C$*foo with its previous value, rather than the caller's value. -The temporized contextual variable takes its read/write policy from -the previous C$*foo container. +C$*foo with its current value, rather than the caller's value. +Also, it is allowed only on read/write contextual variables, since +the only reason to make a copy of the outer value would be +because you'd want to override it later and then forget the +changes at the end of the current dynamic scope. The CCONTEXT package is primarily for internal overriding of contextual information, modelled on how environmental variables work among Modified: docs/Perl6/Spec/S06-routines.pod === --- docs/Perl6/Spec/S06-routines.pod2009-08-31 23:42:06 UTC (rev 28150) +++ docs/Perl6/Spec/S06-routines.pod2009-09-01 00:09:52 UTC (rev 28151) @@ -15,8 +15,8 @@ Created: 21 Mar 2003 -Last Modified: 24 Jul 2009 -Version: 112 +Last Modified: 31 Aug 2009 +Version: 113 This document summarizes Apocalypse 6, which covers subroutines and the @@ -2669,9 +2669,9 @@ C CALLER::$varname specifies the C$varname visible in the dynamic scope from which the current block/closure/subroutine -was called, provided that variable is declared with the Cis context -trait.
