Package com.singularsys.jep.walkers

Class SubstitutionVisitor

  • All Implemented Interfaces:
    JepComponent, ParserVisitor, java.io.Serializable
    public class SubstitutionVisitor
extends DoNothingVisitor
    Allows substitution of variable with values or expressions. For example 
     Jep jep = new Jep();
 SubstitutionVisitor sv = new SubstitutionVisitor(jep);
 Node node = jep.parse("x^2+x");
 Node sub = jep.parse("sin(y)");
 Node res = sv.substitute(node,"x",sub);
    Will give the expression "(sin(y))^2+sin(y)".

    Various different types of substitution are available.

    Substitute a variable by a value.
    substitute(Node, String, Object)
    Substitute a variable by an expression
    substitute(Node, String, Node)
    Substitute a set of variables by a set of values
    substitute(Node, String[], Object[])
    Substitute a set of variables by a set of expressions
    substitute(Node, String[], String[])
    Substitute using an expression of the form x=z+3
    substitute(Node, Node)
    Substitute using a set of expressions of the form x=z+3
    substitute(Node, Node[])

    The methods which do multiple substitutions at the same time do not apply substitutions to the expressions which have been substituted. Hence if we try to use two substitutions x=y+2, y=z+3 the result of substituting into x^2+y^2 will be (y+2)^2+(z+3)^2 and not (z+3+2)^2+(z+1)^2. This prevents possible infinite recursion. To completely substitute a set of expressions a loop could be used. 

     Node base = jep.parse("x^2+y^2");
 Node sub1 = jep.parse("x=y+2");
 Node sub2 = jep.parse("y=z+3");
 Node subs[] = new Node[] {sub1,sub2};
 for(Node sub:subs) {
    base = sv.substitute(base, sub);
 }
    Note that the order of substitution matters.
    Author:
    Rich Morris Created on 16-Nov-2003
    See Also:
    Serialized Form

    • Constructor Detail

      • SubstitutionVisitor

        public SubstitutionVisitor​(Jep j)

      • SubstitutionVisitor

        public SubstitutionVisitor()
        Constructor to uses as a JepComponent. init(Jep) method must be called to set the jep instance.
        Since:
        3.4.0

    • Method Detail

      • init

        public void init​(Jep j)
        Description copied from interface: JepComponent
        Initialize the component. This methods is called whenever a component is added to Jep. Hence it allows components to keep track of the other components they may rely on.
        Specified by:
        init in interface JepComponent
        Overrides:
        init in class DoNothingVisitor
        Parameters:
        j - the current Jep instance

      • substitute

        public Node substitute​(Node orig,
                       java.lang.String name,
                       Node replacement)
                throws ParseException
        Substitutes all occurrences of variable var with replacement. Does not do a DeepCopy.
        Parameters:
        orig - the expression we wish to perform the substitution on
        name - the name of the variable
        replacement - the expression var is substituted for
        Returns:
        the tree with variable replace (does not do a DeepCopy)
        Throws:
        ParseException

      • substitute

        public Node substitute​(Node orig,
                       Node sub)
                throws ParseException
        Substitutes into orig the equation given by sub
        Parameters:
        orig - the equation to substitute into
        sub - and equation of the form x=....
        Returns:
        a copy of orig after substitution
        Throws:
        ParseException - if sub is of the wrong form

      • substitute

        public Node substitute​(Node orig,
                       Node[] subs)
                throws ParseException
        Substitute a set of equations into the original. For example 
         
        Node base = jep.parse("x^2+y^2");
        Node sub1 = jep.parse("x=y+2");
        Node sub2 = jep.parse("y=z+3");
        Node res = sv.substitute(base, new Node[] {sub1,sub2});
        Node this method does not do two levels of substitution, so the result here is (y+2)^2+(z+3)^2.
        Parameters:
        orig - the expression to substitute into
        subs - a set of equations of the form x=...
        Returns:
        a copy of orig after substitution
        Throws:
        ParseException

      • substitute

        public Node substitute​(Node orig,
                       java.lang.String[] names,
                       Node[] replacements)
                throws ParseException
        Substitutes all occurrences of a set of variables var with a set of replacements. Does not do a DeepCopy. For example 
        
	Node base = jep.parse("x^2+y^2");
	Node sub1 = jep.parse("y+2");
	Node sub2 = jep.parse("z+3");
	Node res = sv.substitute(base, new String[]{"x","y"},new Node[] {sub1,sub2});
        Node this method does not do two levels of substitution, so the result here is (y+2)^2+(z+3)^2.
        Parameters:
        orig - the expression we wish to perform the substitution on
        names - the names of the variable
        replacements - the expression var is substituted for
        Returns:
        the tree with variable replace (does not do a DeepCopy)
        Throws:
        ParseException

      • substitute

        public Node substitute​(Node orig,
                       java.lang.String[] names,
                       java.lang.Object[] values)
                throws ParseException
        Substitute all occurrences of variables with matching name with corresponding values. For example 
        substitute(node, new String[]{"x","y"}, new Double[]{3.0,2.0});
        Parameters:
        orig - the equation to substitute into
        names - set of variable names
        values - set of values
        Returns:
        node with the substitution performed
        Throws:
        ParseException

      • substitute

        public Node substitute​(Node orig,
                       java.lang.String name,
                       java.lang.Object value)
                throws ParseException
        Substitute a single variable with a given value. For example substitute(node, "x", 3.0);
        Parameters:
        orig - equation to perform substitution on
        name - variable name
        value - value to use
        Returns:
        node with the substitution performed
        Throws:
        ParseException
        Since:
        3.4.0

      • substitute

        public Node substitute​(Node orig,
                       java.lang.String[] oldNames,
                       java.lang.String[] newNames)
                throws ParseException
        Renames a set of variables with a new set of names.
        Parameters:
        orig - equation to perform substitution on
        oldNames - the old variable name
        newNames - the new variable names
        Returns:
        node with the substitution performed
        Throws:
        ParseException