CTrans

Basic Constraint Transformation library

Status

Background

CTrans supports basic transformation rules as explained in these lecture notes. A more comprehensive description can be also found here.

Usage

CTrans is a tool for translating a given boolean expression into CNF or DNF, respectively. The boolean expression has to satisfy the following context-free grammar definition.

grammar Logic;

rule_set : expression EOF ;

conclusion : IDENTIFIER ;

expression
 : not expression
 | expression and expression
 | expression or expression
 | expression xor expression
 | expression implies expression
 | LPAREN expression RPAREN
 | atom;

atom : IDENTIFIER
| LPAREN IDENTIFIER RPAREN;

not : 'not';
and : 'and' ;
or : 'or' ;
xor : 'xor';
implies : 'implies';

LPAREN : '(' ;
RPAREN : ')' ;

IDENTIFIER : [a-zA-Z_][a-zA-Z_0-9]*;

WS : [ \r\t\n]+ -> skip ;

The following example illustrates how CTrans can be used in order to translate a given boolean expression a implies d. First, we invoke the method translate() on the static class CTrans that takes as first input the expression that we wish to translate, and as second argument the target format which can be either DNF or CNF. The call to translate() will return an Ast object which is the abstract syntax tree (AST) of translated input expression. In the example below a is the DNF representation of a implies b.

Ast a = CTrans.INSTANCE.translate("a implies d", TranslationTarget.DNF);
System.out.println(a.toDot());

For visualizing the abstract syntax tree, the method toDot() can be invoked on the Ast object which will return a String in dot format; the AST can then be visualized by means of graphviz. For the visualization of the dot files this script might be helpful. For the example expression, the following AST will be generated:

Licence

The MIT License (MIT)

Copyright (c) 2017 Julian Thome julian.thome.de@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.