X-Git-Url: http://git.vpit.fr/?p=perl%2Fmodules%2FScope-Upper.git;a=blobdiff_plain;f=README;h=15bb1ec4605ba4544036305244a377a8aa8cc345;hp=7d441b7558fa36830cac4af0e6297130b6b95c27;hb=HEAD;hpb=70187dc24bb0f90a81f58ff2bd52ba7d9c3ac06f diff --git a/README b/README index 7d441b7..1f7b09e 100644 --- a/README +++ b/README @@ -2,7 +2,7 @@ NAME Scope::Upper - Act on upper scopes. VERSION - Version 0.18 + Version 0.34 SYNOPSIS "reap", "localize", "localize_elem", "localize_delete" and "WORDS" : @@ -148,13 +148,16 @@ DESCRIPTION higher contexts with respectively "localize", "localize_elem" and "localize_delete" ; - * return values immediately to an upper level with "unwind", and know - which context was in use then with "want_at" ; + * return values immediately to an upper level with "unwind", "yield" + and "leave" ; + + * gather information about an upper context with "want_at" and + "context_info" ; * execute a subroutine in the setting of an upper subroutine stack frame with "uplevel" ; - * uniquely identify contextes with "uid" and "validate_uid". + * uniquely identify contexts with "uid" and "validate_uid". FUNCTIONS In all those functions, $context refers to the target scope. @@ -166,11 +169,18 @@ 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 : @@ -223,7 +233,10 @@ 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 @@ -236,7 +249,10 @@ FUNCTIONS will be vivified as soon as the localization occurs and emptied when it ends, although it will still exist in its glob. - "localize_delete $what, $key, $context" + "localize_delete" + localize_delete $what, $key; + localize_delete $what, $key, $context; + Introduces the deletion of a variable or an array/hash element delayed to the time of first return into the upper scope denoted by $context. $what can be: @@ -245,18 +261,23 @@ FUNCTIONS "local *x". * A string beginning with '@' or '%', for which the call is equivalent - to respectiveley "local $a[$key]; delete $a[$key]" and "local + to respectively "local $a[$key]; delete $a[$key]" and "local $h{$key}; delete $h{$key}". * A string beginning with '&', which more or less does "undef &func" in the upper scope. It's actually more powerful, as &func won't even "exists" anymore. $key is ignored. - "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 - an upper scope. + "unwind" + unwind; + unwind @values, $context; + + Returns @values *from* the subroutine, eval or format context pointed by + or just above $context, and immediately restarts the program flow at + this point - thus effectively returning @values to an upper scope. If + @values is empty, then the $context parameter is optional and defaults + to the current context (making the call equivalent to a bare "return;") + ; otherwise it is mandatory. The upper context isn't coerced onto @values, which is hence always evaluated in list context. This means that @@ -269,11 +290,55 @@ FUNCTIONS will set $num to 'z'. You can use "want_at" to handle these cases. - "want_at $context" - Like "wantarray", but for the subroutine/eval/format at or just above - $context. + "yield" + yield; + yield @values, $context; + + Returns @values *from* the context pointed by or just above $context, + and immediately restarts the program flow at this point. If @values is + empty, then the $context parameter is optional and defaults to the + current context ; otherwise it is mandatory. + + "yield" differs from "unwind" in that it can target *any* upper scope + (besides a "s///e" substitution context) and not necessarily a sub, an + eval or a format. Hence you can use it to return values from a "do" or a + "map" block : + + my $now = do { + local $@; + eval { require Time::HiRes } or yield time() => HERE; + Time::HiRes::time(); + }; + + my @uniq = map { + yield if $seen{$_}++; # returns the empty list from the block + ... + } @things; + + Like for "unwind", the upper context isn't coerced onto @values. You can + use the fifth value returned by "context_info" to handle context + coercion. + + "leave" + leave; + leave @values; - The previous example can then be "corrected" : + Immediately returns @values from the current block, whatever it may be + (besides a "s///e" substitution context). "leave" is actually a synonym + for "yield HERE", while "leave @values" is a synonym for "yield @values, + HERE". + + Like for "yield", you can use the fifth value returned by "context_info" + to handle context coercion. + + "want_at" + my $want = want_at; + my $want = want_at $context; + + Like "wantarray" in perlfunc, but for the subroutine, eval or format + context located at or just above $context. + + It can be used to revise the example showed in "unwind" : my $num = sub { my @a = ('a' .. 'z'); @@ -283,8 +348,57 @@ FUNCTIONS will rightfully set $num to 26. - "uplevel $code, @args, $context" - Executes the code reference $code with arguments @args as if it were + "context_info" + my ($package, $filename, $line, $subroutine, $hasargs, + $wantarray, $evaltext, $is_require, $hints, $bitmask, + $hinthash) = context_info $context; + + Gives information about the context denoted by $context, akin to what + "caller" in perlfunc provides but not limited only to subroutine, eval + and format contexts. When $context is omitted, it defaults to the + current context. + + The returned values are, in order : + + * *(index 0)* : the namespace in use when the context was created ; + + * *(index 1)* : the name of the file at the point where the context + was created ; + + * *(index 2)* : the line number at the point where the context was + created ; + + * *(index 3)* : the name of the subroutine called for this context, or + "undef" if this is not a subroutine context ; + + * *(index 4)* : a boolean indicating whether a new instance of @_ was + set up for this context, or "undef" if this is not a subroutine + context ; + + * *(index 5)* : the context (in the sense of "wantarray" in perlfunc) + in which the context (in our sense) is executed ; + + * *(index 6)* : the contents of the string being compiled for this + context, or "undef" if this is not an eval context ; + + * *(index 7)* : a boolean indicating whether this eval context was + created by "require", or "undef" if this is not an eval context ; + + * *(index 8)* : the value of the lexical hints in use when the context + was created ; + + * *(index 9)* : a bit string representing the warnings in use when the + context was created ; + + * *(index 10)* : a reference to the lexical hints hash in use when the + context was created (only on perl 5.10 or greater). + + "uplevel" + my @ret = uplevel { ...; return @ret }; + my @ret = uplevel { my @args = @_; ...; return @ret } @args, $context; + my @ret = &uplevel($callback, @args, $context); + + Executes the code reference $callback 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 @@ -303,6 +417,9 @@ FUNCTIONS my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25) my $count = target(1, 2, 4); # $count is 3 + Note that if @args is empty, then the $context parameter is optional and + defaults to the current context ; otherwise it is mandatory. + Sub::Uplevel also implements a pure-Perl version of "uplevel". Both are identical, with the following caveats : @@ -352,7 +469,10 @@ FUNCTIONS Albeit the three exceptions listed above, it passes all the tests of Sub::Uplevel. - "uid $context" + "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 @@ -401,7 +521,9 @@ FUNCTIONS To check whether a given UID is valid, you can use the "validate_uid" function. - "validate_uid $uid" + "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). @@ -431,39 +553,71 @@ 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. + omitted, it defaults to the current context. + + "UP" + my $upper_context = UP; + my $upper_context = UP $from; - "UP $from" - The context of the scope just above $from. + The context of the scope just above $from. If $from points to the + top-level scope in the current stack, then a warning is emitted and + $from is returned (see "DIAGNOSTICS" for details). - "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". + "SUB" + my $sub_context = SUB; + my $sub_context = SUB $from; - "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". + The context of the closest subroutine above $from. If $from already + designates a subroutine context, then it is returned as-is ; hence "SUB + SUB == SUB". If no subroutine context is present in the call stack, then + a warning is emitted and the current context is returned (see + "DIAGNOSTICS" for details). + + "EVAL" + my $eval_context = EVAL; + my $eval_context = EVAL $from; + + The context of the closest eval above $from. If $from already designates + an eval context, then it is returned as-is ; hence "EVAL EVAL == EVAL". + If no eval context is present in the call stack, then a warning is + emitted and the current context is returned (see "DIAGNOSTICS" for + details). Getting a context from a level Here, $level should denote a number of scopes above the current one. When omitted, it defaults to 0 and those functions return the same context as "HERE". - "SCOPE $level" - The $level-th upper context, regardless of its type. + "SCOPE" + my $context = SCOPE; + my $context = SCOPE $level; + + The $level-th upper context, regardless of its type. If $level points + above the top-level scope in the current stack, then a warning is + emitted and the top-level context is returned (see "DIAGNOSTICS" for + details). + + "CALLER" + my $context = CALLER; + my $context = CALLER $level; - "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 - the top scope in the current context. + the top scope in the current context. If $level points above the + top-level scope in the current stack, then a warning is emitted and the + top-level context is returned (see "DIAGNOSTICS" for details). Examples Where "reap" fires depending on the $cxt : @@ -506,13 +660,15 @@ WORDS # $cxt = SCOPE(4), UP SUB UP SUB = UP SUB EVAL = UP CALLER(2) = TOP ... - Where "unwind", "want_at" and "uplevel" point to depending on the $cxt: + Where "unwind", "yield", "want_at", "context_info" and "uplevel" point + to depending on the $cxt: sub { eval { sub { { - unwind @things => $cxt; # or uplevel { ... } $cxt; + unwind @things => $cxt; # or yield @things => $cxt + # or uplevel { ... } $cxt ... } ... @@ -526,10 +682,25 @@ WORDS # (*) Note that uplevel() will croak if you pass that scope frame, # because it cannot target eval scopes. +DIAGNOSTICS + "Cannot target a scope outside of the current stack" + This warning is emitted when "UP", "SCOPE" or "CALLER" end up pointing + to a context that is above the top-level context of the current stack. + It indicates that you tried to go higher than the main scope, or to + point across a "DESTROY" method, a signal handler, an overloaded or tied + method call, a "require" statement or a "sort" callback. In this case, + the resulting context is the highest reachable one. + + "No targetable %s scope in the current stack" + This warning is emitted when you ask for an "EVAL" or "SUB" context and + no such scope can be found in the call stack. The resulting context is + the current one. + EXPORT The functions "reap", "localize", "localize_elem", "localize_delete", - "unwind", "want_at" and "uplevel" are only exported on request, either - individually or by the tags ':funcs' and ':all'. + "unwind", "yield", "leave", "want_at", "context_info" 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'. @@ -539,6 +710,11 @@ EXPORT ':words' and ':all'. CAVEATS + It is not possible to act upon a scope that belongs to another perl + 'stack', i.e. to target a scope across a "DESTROY" method, a signal + handler, an overloaded or tied method call, a "require" statement or a + "sort" callback. + Be careful that local variables are restored in the reverse order in which they were localized. Consider those examples: @@ -586,15 +762,25 @@ CAVEATS 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 + 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. + Starting from "perl" 5.19.4, it is unfortunately no longer possible to + reliably throw exceptions from "uplevel"'d code while the debugger is in + use. This may be solved in a future version depending on how the core + evolves. + DEPENDENCIES - XSLoader (standard since perl 5.006). + perl 5.6.1. + + A C compiler. This module may happen to build with a C++ compiler as + well, but don't rely on it, as no guarantee is made in this regard. + + XSLoader (core since perl 5.6.0). SEE ALSO "local" in perlfunc, "Temporary Values via local()" in perlsub. @@ -611,7 +797,7 @@ SEE ALSO Scope::Escape. AUTHOR - Vincent Pit, "", . + Vincent Pit "". You can contact me by mail or on "irc.perl.org" (vincent). @@ -627,16 +813,19 @@ SUPPORT perldoc Scope::Upper - Tests code coverage report is available at - . - ACKNOWLEDGEMENTS Inspired by Ricardo Signes. + The reimplementation of a large part of this module for perl 5.24 was + provided by David Mitchell. His work was sponsored by the Perl 5 Core + Maintenance Grant from The Perl Foundation. + Thanks to Shawn M. Moore for motivation. COPYRIGHT & LICENSE - Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved. + Copyright + 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2021,2023 + 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.