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B::Generate(3)	      User Contributed Perl Documentation	B::Generate(3)

NAME
       B::Generate - Create your own op	trees.

SYNOPSIS
	   use B::Generate;
	   # Do	nothing, slowly.
	   CHECK {
	       my $null	= new B::OP("null",0);
	       my $enter = new B::OP("enter",0);
	       my $cop = new B::COP(0, "hiya", 0);
	       my $leave = new B::LISTOP("leave", 0, $enter, $null);
	       $leave->children(3);
	       $enter->sibling($cop);
	       $enter->next($cop);
	       $cop->sibling($null);
	       $null->next($leave);
	       $cop->next($leave);

	       # Tell Perl where to find our tree.
	       B::main_root($leave);
	       B::main_start($enter);
	   }

WARNING
       This module will	create segmentation faults if you don't	know how to
       use it properly.	Further	warning: sometimes I don't know	how to use it
       properly.

       There are lots of other methods and utility functions, but they are not
       documented here.	This is	deliberate, rather than	just through laziness.
       You are expected	to have	read the Perl and XS sources to	this module
       before attempting to do anything	with it.

DESCRIPTION
       The "B" module allows you to examine the	Perl op	tree at	runtime, in
       Perl space; it's	the basis of the Perl compiler.	 But what it doesn't
       let you do is manipulate	that op	tree: it won't let you create new ops,
       or modify old ones. Now you can.

       Well, if	you're intimately familiar with	Perl's internals, you can.

       "B::Generate" turns "B"'s accessor methods into get-set methods.
       Hence, instead of merely	saying

	   $op2	= $op->next;

       you can now say

	   $op->next($op2);

       to set the next op in the chain.	It also	adds constructor methods to
       create new ops. This is where it	gets really hairy.

	   new B::OP	 ( type, flags )
	   new B::UNOP	 ( type, flags,	first )
	   new B::BINOP	 ( type, flags,	first, last )
	   new B::LOGOP	 ( type, flags,	first, other )
	   new B::LISTOP ( type, flags,	first, last )
	   new B::SVOP	 ( type, flags,	sv )
	   new B::COP	 ( flags, name,	first )

       In all of the above constructors, "type"	is either a numeric value
       representing the	op type	(62 is the addition operator in	certain	perl
       versions, for instance) or the name of the op. ("add")

       Incidentally, if	you know about custom ops and have registed them
       properly	with the interpreter, you can create custom ops	by name: "new
       B::OP("mycustomop",0)", or whatever.

       "first",	"last" and "other" are ops to be attached to the current op;
       these should be "B::OP" objects.	If you haven't created the ops yet,
       don't worry; give a false value,	and fill them in later:

	   $x =	new B::UNOP("negate", 0, undef);
	   # ... create	some more ops ...
	   $x->first($y);

       In addition, one	may create a new "nextstate" operator with

	   newstate B::op ( flags, label, op)

       in the same manner as "B::COP::new" - this will also, however, add the
       "lineseq" op.

       Finally,	you can	set the	main root and the starting op by passing ops
       to the "B::main_root" and "B::main_start" functions.

       This module can obviously be used for all sorts of fun and
       optimizational purposes.	One example will be in conjuction with source
       filters;	have your source filter	parse an input file in a foreign
       language, create	an op tree for it and get Perl to execute it. Then
       email me	and tell me how	you did	it.  And why.

   OTHER METHODS
       B::SVOP->sv()
	  Returns the SV value instead of the "B::SV" object. For instance:

	      $b_sv = $svop->sv;
	      if ($b_sv->sv == 3) {
		  print	"SVOP's	SV has an IV of	3\n"
	      }

	  But to set the SV you	need a proper B::SV object.

       $op->dump
	  Runs "Perl_op_dump" on an op;	this is	roughly	equivalent to
	  "B::Debug", but not quite.

       $b_sv->dump
	  Runs "Perl_sv_dump" on an SV;	this is	exactly	equivalent to
	  "Devel::Peek::dump($b_sv->sv)"

       $b_op->linklist
	  Sets the "op_next" pointers in the tree in correct execution order,
	  overwriting the old "next" pointers. You need	to do this once	you've
	  created an op	tree for execution, unless you've carefully threaded
	  it together yourself.

       $b_op->scope
	  Create a surrounding scope for the b_op, "parenthesize" it.

	  Creates on OPf_PARENS	(already parenthesized by the parser) a	full
	  lineseq, enter, b_op,	leave sequence.

	  Otherwise just scope,	b_op.

       B::SVOP->new_svrv ( type, flags,	sv )
	  Similar to B::SVOP->new ( type, flags, sv ), it just creates a new
	  SVOP with an attached	sv as SvRV to the given	sv.

       $cv->NEW_with_start (root, start)
	  Clone	the "cv" with new root and start ops. Note that	contrary to
	  "cv_clone", the PADLIST and pad index	is kept, but the index might
	  point	to a different lexical,	because	the PADLIST indices will be
	  different. See t/new_cv.t.

	  Warning: "$cv-"NEW_with_start> is disabled on	some strict platforms,
	  like MSWin32.	 See CPAN RT#28912.

       $b_op->targ ( [ targ] )
	  Get or set the PADOFFSET.

   EXPORT
       None.

AUTHOR
       Simon Cozens, "simon@cpan.org" Reini Urban, "rurban@cpan.org"

MAINTAINERS
       Maintained by Reini Urban.

       This is just a list of people who have submitted	patches	to the module:

       Josh Jore, Michael Schwern, Jim Cromie, Scott Walters, Reini Urban,
       Anton Berezin, Dmitry Karasik.

       Maintainership permissions do have: Artur Bergman, Chia-liang Kao,
       Anton Berezin, Jim Cromie, Joshua ben Jore, Michael G Schwern, Matt S
       Trout, Reini Urban, Scott Walters.

LICENSE
       This module is available	under the same licences	as perl, the Artistic
       license and the GPL.

SEE ALSO
       B, perlguts, op.c, perloptree with B::C

perl v5.24.1			  2017-02-23			B::Generate(3)

NAME | SYNOPSIS | WARNING | DESCRIPTION | AUTHOR | MAINTAINERS | LICENSE | SEE ALSO

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