/ 
Parse-Eyapp-1.132
River stage one • 1 direct dependent • 4 total dependents
/ treereg

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 syntaxis 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.

EXAMPLE

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

  ----------------------------------------------------------
  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 it using eyapp:

----------------------------------------------------------
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 consider this tree grammar:

----------------------------------------------------------
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 it with treereg:

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

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

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

SEE ALSO

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.