X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2Foverload.pm;h=c5ac87aef70d1723e70cee95098f51d24d3b797c;hb=2b393bf410d9f1bf0b80132c4e8b5d6707a139f8;hp=21a4b671ffc1cefbc0a29b182acf7e6a55b2dca0;hpb=88c28ceba84d380fbac88f13c3dfcca0d1b7f014;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/overload.pm b/lib/overload.pm index 21a4b67..c5ac87a 100644 --- a/lib/overload.pm +++ b/lib/overload.pm @@ -1,8 +1,6 @@ package overload; -our $VERSION = '1.00'; - -$overload::hint_bits = 0x20000; +our $VERSION = '1.07'; sub nil {} @@ -74,7 +72,13 @@ sub OverloadedStringify { sub Method { my $package = shift; - $package = ref $package if ref $package; + if(ref $package) { + local $@; + local $!; + require Scalar::Util; + $package = Scalar::Util::blessed($package); + return undef if !defined $package; + } #my $meth = $package->can('(' . shift); ov_method mycan($package, '(' . shift), $package; #return $meth if $meth ne \&nil; @@ -84,35 +88,41 @@ sub Method { sub AddrRef { my $package = ref $_[0]; return "$_[0]" unless $package; - bless $_[0], overload::Fake; # Non-overloaded package - my $str = "$_[0]"; - bless $_[0], $package; # Back - $package . substr $str, index $str, '='; -} -sub StrVal { - (OverloadedStringify($_[0]) or ref($_[0]) eq 'Regexp') ? - (AddrRef(shift)) : - "$_[0]"; + local $@; + local $!; + require Scalar::Util; + my $class = Scalar::Util::blessed($_[0]); + my $class_prefix = defined($class) ? "$class=" : ""; + my $type = Scalar::Util::reftype($_[0]); + my $addr = Scalar::Util::refaddr($_[0]); + return sprintf("$class_prefix$type(0x%x)", $addr); } +*StrVal = *AddrRef; + sub mycan { # Real can would leave stubs. my ($package, $meth) = @_; - return \*{$package . "::$meth"} if defined &{$package . "::$meth"}; - my $p; - foreach $p (@{$package . "::ISA"}) { - my $out = mycan($p, $meth); - return $out if $out; + + local $@; + local $!; + require mro; + + my $mro = mro::get_linear_isa($package); + foreach my $p (@$mro) { + my $fqmeth = $p . q{::} . $meth; + return \*{$fqmeth} if defined &{$fqmeth}; } + return undef; } %constants = ( - 'integer' => 0x1000, - 'float' => 0x2000, - 'binary' => 0x4000, - 'q' => 0x8000, - 'qr' => 0x10000, + 'integer' => 0x1000, # HINT_NEW_INTEGER + 'float' => 0x2000, # HINT_NEW_FLOAT + 'binary' => 0x4000, # HINT_NEW_BINARY + 'q' => 0x8000, # HINT_NEW_STRING + 'qr' => 0x10000, # HINT_NEW_RE ); %ops = ( with_assign => "+ - * / % ** << >> x .", @@ -120,7 +130,7 @@ sub mycan { # Real can would leave stubs. num_comparison => "< <= > >= == !=", '3way_comparison'=> "<=> cmp", str_comparison => "lt le gt ge eq ne", - binary => "& | ^", + binary => '& &= | |= ^ ^=', unary => "neg ! ~", mutators => '++ --', func => "atan2 cos sin exp abs log sqrt int", @@ -140,7 +150,7 @@ sub constant { elsif (!exists $constants {$_ [0]}) { warnings::warnif ("`$_[0]' is not an overloadable type"); } - elsif (!ref $_ [1] || "$_[1]" !~ /CODE\(0x[\da-f]+\)$/) { + elsif (!ref $_ [1] || "$_[1]" !~ /(^|=)CODE\(0x[0-9a-f]+\)$/) { # Can't use C above as code references can be # blessed, and C would return the package the ref is blessed into. if (warnings::enabled) { @@ -150,7 +160,7 @@ sub constant { } else { $^H{$_[0]} = $_[1]; - $^H |= $constants{$_[0]} | $overload::hint_bits; + $^H |= $constants{$_[0]}; } shift, shift; } @@ -171,7 +181,7 @@ __END__ =head1 NAME -overload - Package for overloading perl operations +overload - Package for overloading Perl operations =head1 SYNOPSIS @@ -184,7 +194,7 @@ overload - Package for overloading perl operations ... package main; - $a = new SomeThing 57; + $a = SomeThing->new( 57 ); $b=5+$a; ... if (overload::Overloaded $b) {...} @@ -298,7 +308,7 @@ if C<+=> is not overloaded. =back -B Due to the presense of assignment versions of operations, +B Due to the presence of assignment versions of operations, routines which may be called in assignment context may create self-referential structures. Currently Perl will not free self-referential structures until cycles are C broken. You may get problems @@ -333,9 +343,9 @@ The following symbols can be specified in C directive: "**", "**=", "<<", "<<=", ">>", ">>=", "x", "x=", ".", ".=", For these operations a substituted non-assignment variant can be called if -the assignment variant is not available. Methods for operations "C<+>", -"C<->", "C<+=>", and "C<-=>" can be called to automatically generate -increment and decrement methods. The operation "C<->" can be used to +the assignment variant is not available. Methods for operations C<+>, +C<->, C<+=>, and C<-=> can be called to automatically generate +increment and decrement methods. The operation C<-> can be used to autogenerate missing methods for unary minus or C. See L<"MAGIC AUTOGENERATION">, L<"Calling Conventions for Mutators"> and @@ -353,12 +363,16 @@ arrays, C is used to compare values subject to C. =item * I - "&", "^", "|", "neg", "!", "~", + "&", "&=", "^", "^=", "|", "|=", "neg", "!", "~", -"C" stands for unary minus. If the method for C is not +C stands for unary minus. If the method for C is not specified, it can be autogenerated using the method for -subtraction. If the method for "C" is not specified, it can be -autogenerated using the methods for "C", or "C<\"\">", or "C<0+>". +subtraction. If the method for C is not specified, it can be +autogenerated using the methods for C, or C<"">, or C<0+>. + +The same remarks in L<"Arithmetic operations"> about +assignment-variants and autogeneration apply for +bit operations C<"&">, C<"^">, and C<"|"> as well. =item * I @@ -382,11 +396,11 @@ C<0+>. =item * I - "bool", "\"\"", "0+", + 'bool', '""', '0+', If one or two of these operations are not overloaded, the remaining ones can be used instead. C is used in the flow control operators -(like C) and for the ternary "C" operation. These functions can +(like C) and for the ternary C operation. These functions can return any arbitrary Perl value. If the corresponding operation for this value is overloaded too, that operation will be called again with this value. @@ -404,6 +418,9 @@ glob (which may require a stringification). The same overloading happens both for the I syntax C$varE> and I syntax C${var}E>. +B Even in list context, the iterator is currently called only +once and with scalar context. + =item * I '${}', '@{}', '%{}', '&{}', '*{}'. @@ -420,7 +437,7 @@ The dereference operators must be specified explicitly they will not be passed t =item * I - "nomethod", "fallback", "=", + "nomethod", "fallback", "=", "~~", see L>. @@ -437,7 +454,7 @@ A computer-readable form of the above table is available in the hash num_comparison => '< <= > >= == !=', '3way_comparison'=> '<=> cmp', str_comparison => 'lt le gt ge eq ne', - binary => '& | ^', + binary => '& &= | |= ^ ^=', unary => 'neg ! ~', mutators => '++ --', func => 'atan2 cos sin exp abs log sqrt', @@ -540,6 +557,11 @@ C<"nomethod"> value, and if this is missing, raises an exception. B C<"fallback"> inheritance via @ISA is not carved in stone yet, see L<"Inheritance and overloading">. +=head2 Smart Match + +The key C<"~~"> allows you to override the smart matching used by +the switch construct. See L. + =head2 Copy Constructor The value for C<"="> is a reference to a function with three @@ -570,7 +592,8 @@ appear as lvalue when the above code is executed. If the copy constructor is required during the execution of some mutator, but a method for C<'='> was not specified, it can be autogenerated as a -string copy if the object is a plain scalar. +string copy if the object is a plain scalar or a simple assignment if it +is not. =over 5 @@ -657,10 +680,28 @@ C=E> or C: =item I can be expressed in terms of an assignment to the dereferenced value, if this -value is a scalar and not a reference. +value is a scalar and not a reference, or simply a reference assignment +otherwise. =back +=head1 Minimal set of overloaded operations + +Since some operations can be automatically generated from others, there is +a minimal set of operations that need to be overloaded in order to have +the complete set of overloaded operations at one's disposal. +Of course, the autogenerated operations may not do exactly what the user +expects. See L above. The minimal set is: + + + - * / % ** << >> x + <=> cmp + & | ^ ~ + atan2 cos sin exp log sqrt int + +Additionally, you need to define at least one of string, boolean or +numeric conversions because any one can be used to emulate the others. +The string conversion can also be used to emulate concatenation. + =head1 Losing overloading The restriction for the comparison operation is that even if, for example, @@ -698,7 +739,10 @@ Package C provides the following public functions: =item overload::StrVal(arg) -Gives string value of C as in absence of stringify overloading. +Gives string value of C as in absence of stringify overloading. If you +are using this to get the address of a reference (useful for checking if two +references point to the same thing) then you may be better off using +C, which is faster. =item overload::Overloaded(arg) @@ -712,12 +756,12 @@ Returns C or a reference to the method that implements C. =head1 Overloading constants -For some application Perl parser mangles constants too much. It is possible -to hook into this process via overload::constant() and overload::remove_constant() -functions. +For some applications, the Perl parser mangles constants too much. +It is possible to hook into this process via C +and C functions. These functions take a hash as an argument. The recognized keys of this hash -are +are: =over 8 @@ -773,9 +817,6 @@ From these methods they may be called as overload::constant integer => sub {Math::BigInt->new(shift)}; } -B Currently overloaded-ness of constants does not propagate -into C. - =head1 IMPLEMENTATION What follows is subject to change RSN. @@ -852,7 +893,7 @@ C<$a = $b> values of $a and $b become I. On the other hand, anyone who has used algebraic notation knows the expressive power of the arithmetic metaphor. Overloading works hard to enable this metaphor while preserving the Perlian way as far as -possible. Since it is not not possible to freely mix two contradicting +possible. Since it is not possible to freely mix two contradicting metaphors, overloading allows the arithmetic way to write things I. The way it is done is described in L. @@ -861,7 +902,7 @@ If some mutator methods are directly applied to the overloaded values, one may need to I other values which references the same value: - $a = new Data 23; + $a = Data->new(23); ... $b = $a; # $b is "linked" to $a ... @@ -870,13 +911,13 @@ same value: Note that overloaded access makes this transparent: - $a = new Data 23; + $a = Data->new(23); $b = $a; # $b is "linked" to $a $a += 4; # would unlink $b automagically However, it would not make - $a = new Data 23; + $a = Data->new(23); $a = 4; # Now $a is a plain 4, not 'Data' preserve "objectness" of $a. But Perl I a way to make assignments @@ -906,7 +947,7 @@ Put this in F in your Perl library directory: Use it as follows: require two_face; - my $seven = new two_face ("vii", 7); + my $seven = two_face->new("vii", 7); printf "seven=$seven, seven=%d, eight=%d\n", $seven, $seven+1; print "seven contains `i'\n" if $seven =~ /i/; @@ -919,10 +960,7 @@ numeric value.) This prints: =head2 Two-face references Suppose you want to create an object which is accessible as both an -array reference and a hash reference, similar to the -L -builtin Perl type. Let's make it better than a pseudo-hash by -allowing index 0 to be treated as a normal element. +array reference and a hash reference. package two_refs; use overload '%{}' => \&gethash, '@{}' => sub { $ {shift()} }; @@ -956,7 +994,7 @@ allowing index 0 to be treated as a normal element. Now one can access an object using both the array and hash syntax: - my $bar = new two_refs 3,4,5,6; + my $bar = two_refs->new(3,4,5,6); $bar->[2] = 11; $bar->{two} == 11 or die 'bad hash fetch'; @@ -969,7 +1007,7 @@ TIEHASH() method is a scalar reference. Second, we create a new tied hash each time the hash syntax is used. This allows us not to worry about a possibility of a reference loop, -would would lead to a memory leak. +which would lead to a memory leak. Both these problems can be cured. Say, if we want to overload hash dereference on a reference to an object which is I as a @@ -1061,15 +1099,15 @@ This module is very unusual as overloaded modules go: it does not provide any usual overloaded operators, instead it provides the L operator C. In this example the corresponding subroutine returns an object which encapsulates operations done over -the objects: C contains C<['n', 3]>, C<2 + new -symbolic 3> contains C<['+', 2, ['n', 3]]>. +the objects: C<< symbolic->new(3) >> contains C<['n', 3]>, C<< 2 + +symbolic->new(3) >> contains C<['+', 2, ['n', 3]]>. Here is an example of the script which "calculates" the side of circumscribed octagon using the above package: require symbolic; my $iter = 1; # 2**($iter+2) = 8 - my $side = new symbolic 1; + my $side = symbolic->new(1); my $cnt = $iter; while ($cnt--) { @@ -1084,7 +1122,7 @@ The value of $side is Note that while we obtained this value using a nice little script, there is no simple way to I this value. In fact this value may -be inspected in debugger (see L), but ony if +be inspected in debugger (see L), but only if C Bption is set, and not via C

command. If one attempts to print this value, then the overloaded operator @@ -1135,7 +1173,7 @@ which outputs and one can inspect the value in debugger using all the possible methods. -Something is is still amiss: consider the loop variable $cnt of the +Something is still amiss: consider the loop variable $cnt of the script. It was a number, not an object. We cannot make this value of type C, since then the loop will not terminate. @@ -1193,8 +1231,8 @@ explicit recursion in num()? (Answer is at the end of this section.) Use this module like this: require symbolic; - my $iter = new symbolic 2; # 16-gon - my $side = new symbolic 1; + my $iter = symbolic->new(2); # 16-gon + my $side = symbolic->new(1); my $cnt = $iter; while ($cnt) { @@ -1314,8 +1352,8 @@ To see it in action, add a method to the package C. After this change one can do - my $a = new symbolic 3; - my $b = new symbolic 4; + my $a = symbolic->new(3); + my $b = symbolic->new(4); my $c = sqrt($a**2 + $b**2); and the numeric value of $c becomes 5. However, after calling @@ -1364,6 +1402,11 @@ and $b. Ilya Zakharevich EFE. +=head1 SEE ALSO + +The L pragma can be used to enable or disable overloaded +operations within a lexical scope. + =head1 DIAGNOSTICS When Perl is run with the B<-Do> switch or its equivalent, overloading