Examples of jmathexpr.util.pattern.ExpressionPattern

jmathexpr.util.pattern.ExpressionPattern
This interface represents an expression pattern that can be used to find matching expressions. A pattern matches an expression if the expression is built from the parts defined by the pattern. Each implementation must also implement Expression so that they can be used as operation arguments. @author Elemér Furka

         */
        private class Addition extends SubRule {


            @Override
            public boolean matches(Expression expr) {
                ExpressionPattern sum = new Sum(s, a);
                
                return new Equality(sum, b).matches(expr);
            }

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         */
        private class Difference extends SubRule {


            @Override
            public boolean matches(Expression expr) {
                ExpressionPattern diff = new Subtraction(s, a);
                
                return new Equality(diff, b).matches(expr);
            }

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        return (lhsIsLinear && (rhs.isConstant() || rhsIsLinear))
                || (rhsIsLinear && (lhs.isConstant() || lhsIsLinear));
    }
    
    public static boolean isLinear(Expression expr, Variable x) {
        ExpressionPattern pattern = new PolynomialTermPattern(x, 1);
        
        if (pattern.matches(expr)) {
            return true;
        } else if (expr instanceof Negation) {
            return isLinear(((Negation) expr).getChild(), x);
        } else if (expr instanceof Division) {
            Expression lhs = ((Division) expr).lhs();

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         */
        private class SqrtAdd extends SubRule {


            @Override
            public boolean matches(Expression expr) {
                ExpressionPattern sum = new Sum(s, a);
                
                return new Equality(sum, b).matches(expr);
            }

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         */
        private class SqrtSubtract extends SubRule {


            @Override
            public boolean matches(Expression expr) {
                ExpressionPattern diff = new Subtraction(s, a);
                
                return new Equality(diff, b).matches(expr);
            }

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    private static Polynomial toPolynomial(Multiplication term, Variable x) {
        NavigableMap<NaturalNumber, Expression> coeffs = new TreeMap();
        TerminationPattern c = Numbers.constant("c");
        TerminationPattern n = Numbers.constant("n");
        ExpressionPattern cxn = new Multiplication(c, new Exponentiation(x, n));


        if (cxn.matches(term)) {
            coeffs.put((NaturalNumber) n.hit(), c.hit());
        } else {
            throw new IllegalArgumentException("Illegal polynomial term: " + term);
        }

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    private Map<Expression, List<ANumber>> selectConstants(List<Expression> evaluated) {
        Map<Expression, List<ANumber>> selected = new HashMap(); // ai*c -> a1, a2, ... an
        NumberPattern a = new NumberPattern();
        TerminationPattern c = new Constant();
        ExpressionPattern p = new Multiplication(a, c);
        
        for (Expression e : evaluated) {
            if (e.isConstant()) {
                if (e instanceof ANumber) { // 1 -> numbers
                    addToSelectionMap(selected, Naturals.one(), (ANumber) e);
                } else if (p.matches(e)) {
                    addToSelectionMap(selected, c.hit(), a.hit());
                } else {
                    addToSelectionMap(selected, e, Naturals.one());
                }
            }

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    private Map<Expression, List<Expression>> selectLikeTerms(List<Expression> evaluated) {
        Map<Expression, List<Expression>> selected = new HashMap(); // ai*f(x) -> a1, a2, ... an
        TerminationPattern c = new Constant();
        TerminationPattern f = new FunctionPattern(new Variable());
        ExpressionPattern p = new Multiplication(c, f);
        
        for (Expression e : evaluated) {
            if (e.isConstant()) {
                continue;
            } else if (p.matches(e)) {
                addToSelectionMap(selected, f.hit(), c.hit());
            } else {
                addToSelectionMap(selected, e, Naturals.one());
            }
        }

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            return false;
        }
    
        private boolean hasMatchingTerm() {
            ExpressionPattern p;
            Expression e;
            
            for (int i = 0; i < terms.size(); i++) { // looping over the patterns...
                if (matchingPatterns.containsKey(i)) {
                    continue;
                }
                
                p = (ExpressionPattern) terms.get(i);
                
                if (p instanceof AnyPattern && i == terms.size() - 1) {
                    Sum rest = new Sum(expressions);
                    
                    return p.matches(rest);
                }
                
                for (int j = 0; j < expressions.size(); j++) { // ... to find a matching term
                    e = expressions.get(j);


                    if (p.matches(e)) {
                        matchingPatterns.put(i, e);
                        expressions.remove(j);


                        return true;
                    }

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                && (lhs.isConstant() || LinearEquation.isLinear(lhs, x) || lhsIsQuadratic));
    }
    
    private static boolean isQuadratic(Expression expr, Variable x) {
        NaturalNumber two = Naturals.getInstance().create(2);
        ExpressionPattern pattern = new PolynomialTermPattern(x, 2);
        
        if (pattern.matches(expr)) {
            return true;
        } else if (expr instanceof Negation) {
            return isQuadratic(((Negation) expr).getChild(), x);
        } else if (expr instanceof Division) {
            Expression lhs = ((Division) expr).lhs();

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