X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2Foverload.pm;h=425da1bf053b2fa8cce8d27aec6c578db52567c2;hb=1e9bd1186a044d6e3506ed14fbe055b8f75f7641;hp=bead929ddd4df1c0d7b0c6e30a085d90fd604c6b;hpb=b267980ddb40b015c095b6e55ef52f73a92b67b0;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/overload.pm b/lib/overload.pm index bead929..425da1b 100644 --- a/lib/overload.pm +++ b/lib/overload.pm @@ -1,6 +1,6 @@ package overload; -$overload::hint_bits = 0x20000; +our $VERSION = '1.07'; sub nil {} @@ -72,7 +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; @@ -82,35 +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 &{$fqmeth}; } + return undef; } %constants = ( - 'integer' => 0x1000, - 'float' => 0x2000, - 'binary' => 0x4000, - 'q' => 0x8000, - 'qr' => 0x10000, + 'integer' => 0x1000, # HINT_NEW_INTEGER + 'float' => 0x2000, # HINT_NEW_FLOAT + 'binary' => 0x4000, # HINT_NEW_BINARY + 'q' => 0x8000, # HINT_NEW_STRING + 'qr' => 0x10000, # HINT_NEW_RE ); %ops = ( with_assign => "+ - * / % ** << >> x .", @@ -118,10 +130,10 @@ sub mycan { # Real can would leave stubs. num_comparison => "< <= > >= == !=", '3way_comparison'=> "<=> cmp", str_comparison => "lt le gt ge eq ne", - binary => "& | ^", + binary => '& &= | |= ^ ^=', unary => "neg ! ~", mutators => '++ --', - func => "atan2 cos sin exp abs log sqrt", + func => "atan2 cos sin exp abs log sqrt int", conversion => 'bool "" 0+', iterators => '<>', dereferencing => '${} @{} %{} &{} *{}', @@ -148,7 +160,7 @@ sub constant { } else { $^H{$_[0]} = $_[1]; - $^H |= $constants{$_[0]} | $overload::hint_bits; + $^H |= $constants{$_[0]}; } shift, shift; } @@ -169,7 +181,7 @@ __END__ =head1 NAME -overload - Package for overloading perl operations +overload - Package for overloading Perl operations =head1 SYNOPSIS @@ -296,7 +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 @@ -331,9 +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 @@ -351,12 +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 @@ -368,21 +384,31 @@ postfix form. =item * I - "atan2", "cos", "sin", "exp", "abs", "log", "sqrt", + "atan2", "cos", "sin", "exp", "abs", "log", "sqrt", "int" If C is unavailable, it can be autogenerated using methods for "E" or "E=E" combined with either unary minus or subtraction. +Note that traditionally the Perl function L rounds to 0, thus for +floating-point-like types one should follow the same semantic. If +C is unavailable, it can be autogenerated using the overloading of +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. +As a special case if the overload returns the object itself then it will +be used directly. An overloaded conversion returning the object is +probably a bug, because you're likely to get something that looks like +C. + =item * I "<>" @@ -392,6 +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 '${}', '@{}', '%{}', '&{}', '*{}'. @@ -408,7 +437,7 @@ The dereference operators must be specified explicitly they will not be passed t =item * I - "nomethod", "fallback", "=", + "nomethod", "fallback", "=", "~~", see L>. @@ -425,7 +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', @@ -528,6 +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 @@ -558,7 +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 @@ -645,10 +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, @@ -686,7 +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) @@ -700,12 +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 @@ -761,9 +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. @@ -840,7 +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. @@ -907,10 +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()} }; @@ -957,12 +1007,12 @@ 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 hash itself, the only problem one has to circumvent is how to access -this I hash (as opposed to the I exhibited by +this I hash (as opposed to the I hash exhibited by the overloaded dereference operator). Here is one possible fetching routine: sub access_hash { @@ -974,7 +1024,7 @@ overloaded dereference operator). Here is one possible fetching routine: $out; } -To move creation of the tied hash on each access, one may an extra +To remove creation of the tied hash on each access, one may an extra level of indirection which allows a non-circular structure of references: package two_refs1; @@ -1011,10 +1061,10 @@ level of indirection which allows a non-circular structure of references: $a->[$key]; } -Now if $baz is overloaded like this, then C<$bar> is a reference to a +Now if $baz is overloaded like this, then C<$baz> is a reference to a reference to the intermediate array, which keeps a reference to an actual array, and the access hash. The tie()ing object for the access -hash is also a reference to a reference to the actual array, so +hash is a reference to a reference to the actual array, so =over @@ -1072,7 +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 @@ -1101,7 +1151,7 @@ inside such a method it is not necessary to pretty-print the I $a and $b of an object. In the above subroutine C<"[$meth $a $b]"> is a catenation of some strings and components $a and $b. If these components use overloading, the catenation operator -will look for an overloaded operator C<.>, if not present, it will +will look for an overloaded operator C<.>; if not present, it will look for an overloaded operator C<"">. Thus it is enough to use use overload nomethod => \&wrap, '""' => \&str; @@ -1123,7 +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 $cnt of the script. It was a number, not an object. We cannot make this value of type C, since then the loop will not terminate. @@ -1204,7 +1254,7 @@ mutator methods (C<++>, C<-=> and so on), does not do deep copying (not required without mutators!), and implements only those arithmetic operations which are used in the example. -To implement most arithmetic operations is easy, one should just use +To implement most arithmetic operations is easy; one should just use the tables of operations, and change the code which fills %subr to my %subr = ( 'n' => sub {$_[0]} ); @@ -1226,7 +1276,7 @@ special to make C<+=> and friends work, except filling C<+=> entry of way to know that the implementation of C<'+='> does not mutate the argument, compare L). -To implement a copy constructor, add C<'=' => \&cpy> to C +To implement a copy constructor, add C<< '=' => \&cpy >> to C line, and code (this code assumes that mutators change things one level deep only, so recursive copying is not needed):