B::Deparse 5.8.8

B::Deparse is a Perl compiler backend to produce perl code. SYNOPSIS perl -MO=Deparse[,-d][,-fFILE][,-p][,-q][,-l] [,-sLETTERS][,-xLEVEL] prog.pl B::Deparse is a backend module for the Perl compiler that generates perl source code, based on the internal compiled structure that perl itself creates after parsing a program. The output of B::Deparse wont be exactly the same as the original source, since perl doesnt keep track of comments or whitespace, and there isnt a one-to-one correspondence between perls syntactical constructions and their compiled form, but it will often be close. When you use the -p option, the output also includes parentheses even when they are not required by precedence, which can make it easy to see if perl is parsing your expressions the way you intended. While B::Deparse goes to some lengths to try to figure out what your original program was doing, some parts of the language can still trip it up; it still fails even on some parts of Perls own test suite. If you encounter a failure other than the most common ones described in the BUGS section below, you can help contribute to B::Deparses ongoing development by submitting a bug report with a small example. OPTIONS As with all compiler backend options, these must follow directly after the -MO=Deparse, separated by a comma but not any white space. -d Output data values (when they appear as constants) using Data::Dumper. Without this option, B::Deparse will use some simple routines of its own for the same purpose. Currently, Data::Dumper is better for some kinds of data (such as complex structures with sharing and self-reference) while the built-in routines are better for others (such as odd floating-point values). -fFILE Normally, B::Deparse deparses the main code of a program, and all the subs defined in the same file. To include subs defined in other files, pass the -f option with the filename. You can pass the -f option several times, to include more than one secondary file. (Most of the time you dont want to use it at all.) You can also use this option to include subs which are defined in the scope of a #line directive with two parameters. -l Add #line declarations to the output based on the line and file locations of the original code. -p Print extra parentheses. Without this option, B::Deparse includes parentheses in its output only when they are needed, based on the structure of your program. With -p, it uses parentheses (almost) whenever they would be legal. This can be useful if you are used to LISP, or if you want to see how perl parses your input. If you say if ($var & 0x7f == 65) {print "Gimme an A!"} print ($which ? $a : $b), "n"; $name = $ENV{USER} or "Bob"; B::Deparse,-p will print if (($var & 0)) { print(Gimme an A!) }; (print(($which ? $a : $b)), ???); (($name = $ENV{USER}) or ???) which probably isnt what you intended (the ??? is a sign that perl optimized away a constant value). -P Disable prototype checking. With this option, all function calls are deparsed as if no prototype was defined for them. In other words, perl -MO=Deparse,-P -e sub foo (@) { 1 } foo @x will print sub foo (@) { 1; } &foo(@x); making clear how the parameters are actually passed to foo. -q Expand double-quoted strings into the corresponding combinations of concatenation, uc, ucfirst, lc, lcfirst, quotemeta, and join. For instance, print print "Hello, $world, @ladies, u$gentlemenE, uL$me!"; as print Hello, . $world . , . join($", @ladies) . , . ucfirst($gentlemen) . , . ucfirst(lc $me . !); Note that the expanded form represents the way perl handles such constructions internally -- this option actually turns off the reverse translation that B::Deparse usually does. On the other hand, note that $x = "$y" is not the same as $x = $y: the former makes the value of $y into a string before doing the assignment. -sLETTERS Tweak the style of B::Deparses output. The letters should follow directly after the s, with no space or punctuation. The following options are available: C Cuddle elsif, else, and continue blocks. For example, print if (...) { ... } else { ... } instead of if (...) { ... } else { ... } The default is not to cuddle. iNUMBER Indent lines by multiples of NUMBER columns. The default is 4 columns. T Use tabs for each 8 columns of indent. The default is to use only spaces. For instance, if the style options are -si4T, a line thats indented 3 times will be preceded by one tab and four spaces; if the options were -si8T, the same line would be preceded by three tabs. vSTRING. Print STRING for the value of a constant that cant be determined because it was optimized away (mnemonic: this happens when a constant is used in void context). The end of the string is marked by a period. The string should be a valid perl expression, generally a constant. Note that unless its a number, it probably needs to be quoted, and on a command line quotes need to be protected from the shell. Some conventional values include 0, 1, 42, , foo, and Useless use of constant omitted (which may need to be -sv"Useless use of constant omitted." or something similar depending on your shell). The default is ???. If youre using B::Deparse on a module or other file thats required, you shouldnt use a value that evaluates to false, since the customary true constant at the end of a module will be in void context when the file is compiled as a main program. -xLEVEL Expand conventional syntax constructions into equivalent ones that expose their internal operation. LEVEL should be a digit, with higher values meaning more expansion. As with -q, this actually involves turning off special cases in B::Deparses normal operations. If LEVEL is at least 3, for loops will be translated into equivalent while loops with continue blocks; for instance for ($i = 0; $i < 10; ++$i) { print $i; } turns into $i = 0; while ($i < 10) { print $i; } continue { ++$i } Note that in a few cases this translation cant be perfectly carried back into the source code -- if the loops initializer declares a my variable, for instance, it wont have the correct scope outside of the loop. If LEVEL is at least 5, use declarations will be translated into BEGIN blocks containing calls to require and import; for instance, use strict refs; turns into sub BEGIN { require strict; do { strict->import(refs) }; } If LEVEL is at least 7, if statements will be translated into equivalent expressions using &&, ?: and do {}; for instance print hi if $nice; if ($nice) { print hi; } if ($nice) { print hi; } else { print bye; } turns into $nice and print hi; $nice and do { print hi }; $nice ? do { print hi } : do { print bye }; Long sequences of elsifs will turn into nested ternary operators, which B::Deparse doesnt know how to indent nicely..

Requirements:	No special requirements
Platforms:	Linux
Keyword:	Bdeparse,  Constant,  For Instance,  If Level,  Level,  Libraries,  Mo,  Nice,  Option,  Output,  Perl,  Print,  Programming,  Will Be
Users rating:	0/10