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TREEREG(1)                           User Contributed Perl Documentation                          TREEREG(1)



NAME
       treereg - Compiler for Tree Regular Expressions

SYNOPSIS
         treereg [-m packagename] [[no]syntax] [[no]numbers] [-severity 0|1|2|3] \
                 [-p treeprefix] [-o outputfile] [-lib /path/to/library/] -i filename[.trg]
         treereg [-m packagename] [[no]syntax] [[no]numbers] [-severity 0|1|2|3] \
                 [-p treeprefix] [-lib /path/to/library/] [-o outputfile] filename[.trg]
         treereg -v
         treereg -h

OPTIONS
       Options can be used both with one dash and double dash.  It is not necessary to write the full name
       of the option.  A disambiguation prefix suffices.

       •   "-i[n] filename"

           Input file. Extension ".trg" is assumed if no extension is provided.

       •   "-o[ut] filename"

           Output file. By default is the name of the input file (concatenated with .pm)

       •   "-m[od] packagename"

           Name of the package containing the generated subroutines.  By default is the longest prefix of
           the input file name that conforms to the classic definition of integer "[a-z_A-Z]\w*".

       •   "-l[ib] /path/to/library/"

           Specifies that "/path/to/library/" will be included in @INC.  Useful when the "syntax" option is
           on. Can be inserted as many times as necessary.

       •   "-p[refix] treeprefix"

           Tree nodes automatically generated using "Parse::Eyapp" are objects blessed into the name of the
           production. To avoid crashes the programmer may prefix the class names with a given prefix when
           calling the parser; for example:

             $self->YYParse( yylex => \&_Lexer, yyerror => \&_Error, yyprefix => __PACKAGE__."::")

           The "-prefix treeprefix" option simplifies the process of writing the tree grammar so that
           instead of writing with the full names

            CLASS::TIMES(CLASS::NUM, $x) and { $NUM->{VAL} == 0) => { $NUM }

           it can be written:

            TIMES(NUM, $x) and { $NUM->{VAL} == 0) => { $NUM }

       •   "-n[umbers]"

           Produces "#line" directives.

       •   "-non[umbers]"

           Disable source file line numbering embedded in your parser

       •   "-sy[ntax]"

           Checks that Perl code is syntactically correct.

       •   "-nosy[ntax]"

           Does not check the syntax of Perl code

       •   "-se[verity] number"

           - 0 = Don't  check arity (default). Matching does not check the arity. The actual node being
           visited may have more children.
           - 1 = Check arity. Matching requires the equality of the number of children and the actual node
           and the pattern.
           - 2 = Check arity and give a warning
           - 3 = Check arity, give a warning and exit
       •   "-v[ersion]"

           Gives the version

       •   "-u[sage]"

           Prints the usage info

       •   "-h[elp]"

           Print this help

DESCRIPTION
       "Treereg" translates a tree grammar specification file (default extension ".trg" describing a set of
       tree patterns and the actions to modify them using tree-terms like:

         TIMES(NUM, $x) and { $NUM->{VAL} == 0) => { $NUM }

       which says that wherever an abstract syntax tree representing the product of a numeric expression
       with value 0 times any other kind of expression, the "TIMES" tree can be substituted by its left
       child.

       The compiler produces a Perl module containing the subroutines implementing those sets of pattern-actions. patternactions.
       actions.

EXAMPLE
       Consider the following "eyapp" grammar (see the "Parse::Eyapp" documentation to know more about
       "Parse::Eyapp" grammars):

         ----------------------------------------------------------nereida:~/LEyapp/examples> ---------------------------------------------------------nereida:~/LEyapp/examples>
         nereida:~/LEyapp/examples> cat Rule6.yp
         %{
         use Data::Dumper;
         %}
         %right  '='
         %left   '-' '+'
         %left   '*' '/'
         %left   NEG
         %tree

         %%
         line: exp  { $_[1] }
         ;

         exp:      %name NUM
                     NUM
                 | %name VAR
                   VAR
                 | %name ASSIGN
                   VAR '=' exp
                 | %name PLUS
                   exp '+' exp
                 | %name MINUS
                   exp '-' exp
                 | %name TIMES
                   exp '*' exp
                 | %name DIV
                   exp '/' exp
                 | %name UMINUS
                   '-' exp %prec NEG
                 |   '(' exp ')'  { $_[2] } /* Let us simplify a bit the tree */
         ;

         %%

         sub _Error {
             die  "Syntax error.\n";
         }

         sub _Lexer {
             my($parser)=shift;

                 $parser->YYData->{INPUT}
             or  $parser->YYData->{INPUT} = <STDIN>
             or  return('',undef);

             $parser->YYData->{INPUT}=~s/^\s+//;

             for ($parser->YYData->{INPUT}) {
                 s/^([0-9]+(?:\.[0-9]+)?)// and return('NUM',$1);
                 s/^([A-Za-z][A-Za-z0-9_]*)// and return('VAR',$1);
                 s/^(.)//s and return($1,$1);
             }
         }

         sub Run {
             my($self)=shift;
             $self->YYParse( yylex => \&_Lexer, yyerror => \&_Error );
         }
         ----------------------------------------------------------Compile ---------------------------------------------------------Compile

       Compile it using "eyapp":

         ----------------------------------------------------------nereida:~/LEyapp/examples> ---------------------------------------------------------nereida:~/LEyapp/examples>
         nereida:~/LEyapp/examples> eyapp Rule6.yp
         nereida:~/LEyapp/examples> ls -ltr | tail -1
         -rw-rw----  1 pl users  4976 2006-09-15 19:56 Rule6.pm
         ----------------------------------------------------------Now ---------------------------------------------------------Now

       Now consider this tree grammar:

         ----------------------------------------------------------nereida:~/LEyapp/examples> ---------------------------------------------------------nereida:~/LEyapp/examples>
         nereida:~/LEyapp/examples> cat Transform2.trg
         %{
         my %Op = (PLUS=>'+', MINUS => '-', TIMES=>'*', DIV => '/');
         %}

         fold: 'TIMES|PLUS|DIV|MINUS':bin(NUM($n), NUM($m))
           => {
             my $op = $Op{ref($bin)};
             $n->{attr} = eval  "$n->{attr} $op $m->{attr}";
             $_[0] = $NUM[0];
           }
         zero_times_whatever: TIMES(NUM($x), .) and { $x->{attr} == 0 } => { $_[0] = $NUM }
         whatever_times_zero: TIMES(., NUM($x)) and { $x->{attr} == 0 } => { $_[0] = $NUM }

         /* rules related with times */
         times_zero = zero_times_whatever whatever_times_zero;
         ----------------------------------------------------------Compile ---------------------------------------------------------Compile

       Compile it with "treereg":

         ----------------------------------------------------------nereida:~/LEyapp/examples> ---------------------------------------------------------nereida:~/LEyapp/examples>
         nereida:~/LEyapp/examples> treereg Transform2.trg
         nereida:~/LEyapp/examples> ls -ltr | tail -1
         -rw-rw----  1 pl users  1948 2006-09-15 19:57 Transform2.pm
         ----------------------------------------------------------The ---------------------------------------------------------The

       The following program makes use of both modules "Rule6.pm" and "Transform2.pm":

         ----------------------------------------------------------nereida:~/LEyapp/examples> ---------------------------------------------------------nereida:~/LEyapp/examples>
         nereida:~/LEyapp/examples> cat foldand0rule6_3.pl
         #!/usr/bin/perl -w
         use strict;
         use Rule6;
         use Parse::Eyapp::YATW;
         use Data::Dumper;
         use Transform2;

         $Data::Dumper::Indent = 1;
         my $parser = new Rule6();
         my $t = $parser->Run;
         print "\n***** Before ******\n";
         print Dumper($t);
         $t->s(@Transform2::all);
         print "\n***** After ******\n";
         print Dumper($t);
         ----------------------------------------------------------When ---------------------------------------------------------When

       When the program runs with input "b*(2-2)" produces the following output:

         ----------------------------------------------------------nereida:~/LEyapp/examples> ---------------------------------------------------------nereida:~/LEyapp/examples>
         nereida:~/LEyapp/examples> foldand0rule6_3.pl
         b*(2-2)

         ***** Before ******
         $VAR1 = bless( {
           'children' => [
             bless( {
               'children' => [
                 bless( { 'children' => [], 'attr' => 'b', 'token' => 'VAR' }, 'TERMINAL' )
               ]
             }, 'VAR' ),
             bless( {
               'children' => [
                 bless( { 'children' => [
                     bless( { 'children' => [], 'attr' => '2', 'token' => 'NUM' }, 'TERMINAL' )
                   ]
                 }, 'NUM' ),
                 bless( {
                   'children' => [
                     bless( { 'children' => [], 'attr' => '2', 'token' => 'NUM' }, 'TERMINAL' )
                   ]
                 }, 'NUM' )
               ]
             }, 'MINUS' )
           ]
         }, 'TIMES' );

         ***** After ******
         $VAR1 = bless( {
           'children' => [
             bless( { 'children' => [], 'attr' => 0, 'token' => 'NUM' }, 'TERMINAL' )
           ]
         }, 'NUM' );
         ----------------------------------------------------------See ---------------------------------------------------------See

       See also the section "Compiling: More Options" in Parse::Eyapp  for a more contrived example.

SEE ALSO
       •   Parse::Eyapp,

       •   eyapptut

       •   The pdf file in <http://nereida.deioc.ull.es/~pl/perlexamples/Eyapp.pdf>

       •   <http://nereida.deioc.ull.es/~pl/perlexamples/section_eyappts.html> (Spanish),

       •   eyapp,

       •   treereg,

       •   Parse::yapp,

       •   yacc(1),

       •   bison(1),

       •   the classic book "Compilers: Principles, Techniques, and Tools" by Alfred V. Aho, Ravi Sethi and

       •   Jeffrey D. Ullman (Addison-Wesley 1986)

       •   Parse::RecDescent.

AUTHOR
       Casiano Rodriguez-Leon

LICENSE AND COPYRIGHT
       Copyright (C) 2006 by Casiano Rodriguez-Leon

       This library is free software; you can redistribute it and/or modify it under the same terms as Perl
       itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have
       available.



perl v5.12.5                                     2011-01-30                                       TREEREG(1)