| TREEREG(1) | User Contributed Perl Documentation | TREEREG(1) |
treereg - Compiler for Tree Regular Expressions
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 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.
Input file. Extension ".trg" is assumed if no extension is provided.
Output file. By default is the name of the input file (concatenated with .pm)
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*".
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.
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 }
Produces "#line" directives.
Disable source file line numbering embedded in your parser
Checks that Perl code is syntactically correct.
Does not check the syntax of Perl code
Gives the version
Prints the usage info
Print this help
"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.
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.
Casiano Rodriguez-Leon
Copyright © 2006, 2007, 2008, 2009, 2010, 2011, 2012 Casiano Rodriguez-Leon. Copyright © 2017 William N. Braswell, Jr. All Rights Reserved.
Parse::Yapp is Copyright © 1998, 1999, 2000, 2001, Francois Desarmenien. Parse::Yapp is Copyright © 2017 William N. Braswell, Jr. All Rights Reserved.
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.
Hey! The above document had some coding errors, which are explained below:
| 2017-06-14 | perl v5.34.0 |