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//               The Next Generation Logic Library                       //
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//  Copyright 2015-20xx Christoph Zengler                                //
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package org.logicng.io.parsers;

import org.antlr.v4.runtime.CommonTokenStream;
import org.logicng.formulas.FormulaFactory;

/**
 * A parser for pseudo Boolean formulas.
 * 
 * The syntax for pseudo Boolean formulas in LogicNG is:
 * 

 * {@code $true} for the constant TRUE
 * {@code $false} for the constant FALSE
 * {@code ~} for the negation
 * {@code |} for the disjunction (OR)
 * {@code &} for the conjunction (AND)
 * {@code =>} for the implication
 * {@code <=>} for the equivalence
 * {@code *} for the multiplication of a literal and its coefficient
 * {@code +} for the summation
 * {@code =} for equals
 * {@code <=} for less-equals
 * {@code <} for less than
 * {@code >=} for greater-equals
 * {@code >} for greater than
 * 
 * Brackets are {@code (} and {@code )}.  For variable names, there are the following rules:
 * 
 * must begin with a alphabetic character, {@code _}, {@code @}, or {@code #}
 * can only contain alphanumerical character, {@code _}, or {@code #}
 * {@code @} is only allowed at the beginning of the variable name and is reserved for special internal variables
 * 
 * 
 * A valid pseudo Boolean expression is of the form {@code c_1 * l_1 + ... + c_n * l_n R k} where the {@code c_i} are coefficients,
 * {@code l_i} are literals, and {@code R} is one of {@code =, >, >=, <, <=}.
 * @version 2.4.1
 * @since 1.0
 */
public final class PseudoBooleanParser extends FormulaParser {

    /**
     * Constructs a new parser for pseudo boolean formulas.
     * @param f the formula factory
     */
    public PseudoBooleanParser(final FormulaFactory f) {
        super(f);
        final PseudoBooleanLexer lexer = new PseudoBooleanLexer(null);
        final CommonTokenStream tokens = new CommonTokenStream(lexer);
        final ParserWithFormula parser = new LogicNGPseudoBooleanParser(tokens);
        setLexerAndParser(lexer, parser);
    }
}