X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=README;h=e09bd1230a0ccc5c13b1fd17e90188bb56a9a6c5;hb=dcc300c85d8832a6e0ad6852f68ea4ec5899348d;hp=54b68ffbfde8a517d4c10e1eac61534fcd320d32;hpb=463fb6b2306558e10e95198da1d0bbf0b5256e61;p=perl%2Fmodules%2FScope-Upper.git diff --git a/README b/README index 54b68ff..e09bd12 100644 --- a/README +++ b/README @@ -2,14 +2,17 @@ NAME Scope::Upper - Act on upper scopes. VERSION - Version 0.15 + Version 0.19 SYNOPSIS "reap", "localize", "localize_elem", "localize_delete" and "WORDS" : package Scope; - use Scope::Upper qw; + use Scope::Upper qw< + reap localize localize_elem localize_delete + :words + >; sub new { my ($class, $name) = @_; @@ -51,22 +54,22 @@ SYNOPSIS package UserLand; { - Scope->new("top"); # initializes $UserLand::tag + Scope->new("top"); # initializes $UserLand::tag { Scope->catch; - my $one = 1 + undef; # prints "top: Use of uninitialized value..." + my $one = 1 + undef; # prints "top: Use of uninitialized value..." { Scope->private; eval { require Cwd }; - print $@; # prints "Can't locate Cwd.pm in @INC (@INC contains:) at..." - } + print $@; # prints "Can't locate Cwd.pm in @INC + } # (@INC contains:) at..." - require Cwd; # loads Cwd.pm + require Cwd; # loads Cwd.pm } - } # prints "top: done" + } # prints "top: done" "unwind" and "want_at" : @@ -94,6 +97,47 @@ SYNOPSIS my @stuff = zap(); # @stuff contains qw my $stuff = zap(); # $stuff contains 3 + "uplevel" : + + package Uplevel; + + use Scope::Upper qw; + + sub target { + faker(@_); + } + + sub faker { + uplevel { + my $sub = (caller 0)[3]; + print "$_[0] from $sub()"; + } @_ => CALLER(1); + } + + target('hello'); # "hello from Uplevel::target()" + + "uid" and "validate_uid" : + + use Scope::Upper qw; + + my $uid; + + { + $uid = uid(); + { + if ($uid eq uid(UP)) { # yes + ... + } + if (validate_uid($uid)) { # yes + ... + } + } + } + + if (validate_uid($uid)) { # no + ... + } + DESCRIPTION This module lets you defer actions *at run-time* that will take place when the control flow returns into an upper scope. Currently, you can: @@ -105,7 +149,12 @@ DESCRIPTION "localize_delete" ; * return values immediately to an upper level with "unwind", and know - which context was in use then with "want_at". + which context was in use then with "want_at" ; + + * execute a subroutine in the setting of an upper subroutine stack + frame with "uplevel" ; + + * uniquely identify contextes with "uid" and "validate_uid". FUNCTIONS In all those functions, $context refers to the target scope. @@ -117,11 +166,18 @@ FUNCTIONS which means that you can safely store it at some point and use it when needed, and it will still denote the original scope. - "reap $callback, $context" + "reap" + reap { ... }; + reap { ... } $context; + &reap($callback, $context); + Adds a destructor that calls $callback (in void context) when the upper scope represented by $context ends. - "localize $what, $value, $context" + "localize" + localize $what, $value; + localize $what, $value, $context; + Introduces a "local" delayed to the time of first return into the upper scope denoted by $context. $what can be : @@ -174,7 +230,10 @@ FUNCTIONS implementation detail, this behaviour may change in the future if proved harmful. - "localize_elem $what, $key, $value, $context" + "localize_elem" + localize_elem $what, $key, $value; + localize_elem $what, $key, $value, $context; + Introduces a "local $what[$key] = $value" or "local $what{$key} = $value" delayed to the time of first return into the upper scope denoted by $context. Unlike "localize", $what must be a string and the type of @@ -203,7 +262,10 @@ FUNCTIONS in the upper scope. It's actually more powerful, as &func won't even "exists" anymore. $key is ignored. - "unwind @values, $context" + "unwind" + unwind @values; + unwind @values, $context; + Returns @values *from* the context pointed by $context, i.e. from the subroutine, eval or format at or just above $context, and immediately restart the program flow at this point - thus effectively returning to @@ -220,7 +282,10 @@ FUNCTIONS will set $num to 'z'. You can use "want_at" to handle these cases. - "want_at $context" + "want_at" + my $want = want_at; + my $want = want_at $context; + Like "wantarray", but for the subroutine/eval/format at or just above $context. @@ -234,6 +299,157 @@ FUNCTIONS will rightfully set $num to 26. + "uplevel $code, @args, $context" + my @ret = uplevel { ...; return @ret }; + my @ret = uplevel { my @args = @_; ...; return @ret } @args; + my @ret = uplevel { ... } @args, $context; + my @ret = &uplevel($callback, @args, $context); + + Executes the code reference $code with arguments @args as if it were + located at the subroutine stack frame pointed by $context, effectively + fooling "caller" and "die" into believing that the call actually + happened higher in the stack. The code is executed in the context of the + "uplevel" call, and what it returns is returned as-is by "uplevel". + + sub target { + faker(@_); + } + + sub faker { + uplevel { + map { 1 / $_ } @_; + } @_ => CALLER(1); + } + + my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25) + my $count = target(1, 2, 4); # $count is 3 + + Sub::Uplevel also implements a pure-Perl version of "uplevel". Both are + identical, with the following caveats : + + * The Sub::Uplevel implementation of "uplevel" may execute a code + reference in the context of any upper stack frame. The Scope::Upper + version can only uplevel to a subroutine stack frame, and will croak + if you try to target an "eval" or a format. + + * Exceptions thrown from the code called by this version of "uplevel" + will not be caught by "eval" blocks between the target frame and the + uplevel call, while they will for Sub::Uplevel's version. This means + that : + + eval { + sub { + local $@; + eval { + sub { + uplevel { die 'wut' } CALLER(2); # for Scope::Upper + # uplevel(3, sub { die 'wut' }) # for Sub::Uplevel + }->(); + }; + print "inner block: $@"; + $@ and exit; + }->(); + }; + print "outer block: $@"; + + will print "inner block: wut..." with Sub::Uplevel and "outer block: + wut..." with Scope::Upper. + + * Sub::Uplevel globally overrides the Perl keyword "caller", while + Scope::Upper does not. + + A simple wrapper lets you mimic the interface of "uplevel" in + Sub::Uplevel : + + use Scope::Upper; + + sub uplevel { + my $frame = shift; + my $code = shift; + my $cxt = Scope::Upper::CALLER($frame); + &Scope::Upper::uplevel($code => @_ => $cxt); + } + + Albeit the three exceptions listed above, it passes all the tests of + Sub::Uplevel. + + "uid" + my $uid = uid; + my $uid = uid $context; + + Returns an unique identifier (UID) for the context (or dynamic scope) + pointed by $context, or for the current context if $context is omitted. + This UID will only be valid for the life time of the context it + represents, and another UID will be generated next time the same scope + is executed. + + my $uid; + + { + $uid = uid; + if ($uid eq uid()) { # yes, this is the same context + ... + } + { + if ($uid eq uid()) { # no, we are one scope below + ... + } + if ($uid eq uid(UP)) { # yes, UP points to the same scope as $uid + ... + } + } + } + + # $uid is now invalid + + { + if ($uid eq uid()) { # no, this is another block + ... + } + } + + For example, each loop iteration gets its own UID : + + my %uids; + + for (1 .. 5) { + my $uid = uid; + $uids{$uid} = $_; + } + + # %uids has 5 entries + + The UIDs are not guaranteed to be numbers, so you must use the "eq" + operator to compare them. + + To check whether a given UID is valid, you can use the "validate_uid" + function. + + "validate_uid" + my $is_valid = validate_uid $uid; + + Returns true if and only if $uid is the UID of a currently valid context + (that is, it designates a scope that is higher than the current one in + the call stack). + + my $uid; + + { + $uid = uid(); + if (validate_uid($uid)) { # yes + ... + } + { + if (validate_uid($uid)) { # yes + ... + } + } + } + + if (validate_uid($uid)) { # no + ... + } + CONSTANTS "SU_THREADSAFE" True iff the module could have been built when thread-safety features. @@ -241,23 +457,36 @@ CONSTANTS WORDS Constants "TOP" + my $top_context = TOP; + Returns the context that currently represents the highest scope. "HERE" + my $current_context = HERE; + The context of the current scope. Getting a context from a context For any of those functions, $from is expected to be a context. When omitted, it defaults to the the current context. - "UP $from" + "UP" + my $upper_context = UP; + my $upper_context = UP $from; + The context of the scope just above $from. - "SUB $from" + "SUB" + my $sub_context = SUB; + my $sub_context = SUB $from; + The context of the closest subroutine above $from. Note that $from is returned if it is already a subroutine context ; hence "SUB SUB == SUB". - "EVAL $from" + "EVAL" + my $eval_context = EVAL; + my $eval_context = EVAL $from; + The context of the closest eval above $from. Note that $from is returned if it is already an eval context ; hence "EVAL EVAL == EVAL". @@ -266,10 +495,16 @@ WORDS When omitted, it defaults to 0 and those functions return the same context as "HERE". - "SCOPE $level" + "SCOPE" + my $context = SCOPE; + my $context = SCOPE $level; + The $level-th upper context, regardless of its type. - "CALLER $level" + "CALLER" + my $context = CALLER; + my $context = CALLER $level; + The context of the $level-th upper subroutine/eval/format. It kind of corresponds to the context represented by "caller $level", but while e.g. "caller 0" refers to the caller context, "CALLER 0" will refer to @@ -284,13 +519,13 @@ WORDS { reap \&cleanup => $cxt; ... - } # $cxt = SCOPE(0), or HERE + } # $cxt = SCOPE(0) = HERE ... - }->(); # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0) + }->(); # $cxt = SCOPE(1) = UP = SUB = CALLER(0) ... - }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) ... - }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2) ... Where "localize", "localize_elem" and "localize_delete" act depending on @@ -301,42 +536,45 @@ WORDS sub { { localize '$x' => 1 => $cxt; - # $cxt = SCOPE(0), or HERE + # $cxt = SCOPE(0) = HERE ... } - # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0) + # $cxt = SCOPE(1) = UP = SUB = CALLER(0) ... }->(); - # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) ... }; - # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2) ... }->(); - # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP + # $cxt = SCOPE(4), UP SUB UP SUB = UP SUB EVAL = UP CALLER(2) = TOP ... - Where "unwind" and "want_at" point to depending on the $cxt: + Where "unwind", "want_at" and "uplevel" point to depending on the $cxt: sub { eval { sub { { - unwind @things => $cxt; + unwind @things => $cxt; # or uplevel { ... } $cxt; ... } ... - }->(); # $cxt = SCOPE(0 .. 1), or HERE, or UP, or SUB, or CALLER(0) + }->(); # $cxt = SCOPE(0) = SCOPE(1) = HERE = UP = SUB = CALLER(0) ... - }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) (*) ... - }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2) ... + # (*) Note that uplevel() will croak if you pass that scope frame, + # because it cannot target eval scopes. + EXPORT The functions "reap", "localize", "localize_elem", "localize_delete", - "unwind" and "want_at" are only exported on request, either individually - or by the tags ':funcs' and ':all'. + "unwind", "want_at" and "uplevel" are only exported on request, either + individually or by the tags ':funcs' and ':all'. The constant "SU_THREADSAFE" is also only exported on request, individually or by the tags ':consts' and ':all'. @@ -378,6 +616,28 @@ CAVEATS may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some context-related fixes. + Calling "goto" to replace an "uplevel"'d code frame does not work : + + * for a "perl" older than the 5.8 series ; + + * for a "DEBUGGING" "perl" run with debugging flags set (as in "perl + -D ...") ; + + * when the runloop callback is replaced by another module. + + In those three cases, "uplevel" will look for a "goto &sub" statement in + its callback and, if there is one, throw an exception before executing + the code. + + Moreover, in order to handle "goto" statements properly, "uplevel" + currently has to suffer a run-time overhead proportional to the size of + the the callback in every case (with a small ratio), and proportional to + the size of all the code executed as the result of the "uplevel" call + (including subroutine calls inside the callback) when a "goto" statement + is found in the "uplevel" callback. Despite this shortcoming, this XS + version of "uplevel" should still run way faster than the pure-Perl + version from Sub::Uplevel. + DEPENDENCIES XSLoader (standard since perl 5.006). @@ -386,6 +646,8 @@ SEE ALSO Alias, Hook::Scope, Scope::Guard, Guard. + Sub::Uplevel. + Continuation::Escape is a thin wrapper around Scope::Upper that gives you a continuation passing style interface to "unwind". It's easier to use, but it requires you to have control over the scope where you want @@ -419,7 +681,7 @@ ACKNOWLEDGEMENTS Thanks to Shawn M. Moore for motivation. COPYRIGHT & LICENSE - Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved. + Copyright 2008,2009,2010,2011,2012 Vincent Pit, all rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.