Module io.jenetics.prog
Package io.jenetics.prog.op

Class MathExpr

java.lang.Object
io.jenetics.prog.op.MathExpr
All Implemented Interfaces:
Serializable, Function<Double[],Double>
public final class MathExpr extends Object implements Function<Double[],Double>, Serializable
Contains methods for parsing mathematical expression.
Since:
4.1
Version:
7.1
See Also:

  • Field Details

    • CONST_REWRITER

      public static final TreeRewriter<Op<Double>> CONST_REWRITER
      This tree-rewriter rewrites constant expressions to its single value. 
      final TreeNode<Op<Double>> tree = MathExpr.parseTree("1 + 2*(6 + 7)");
MathExpr.CONST_REWRITER.rewrite(tree);
assertEquals(tree.getValue(), Const.of(27.0));
      Since:
      5.0

    • ARITHMETIC_REWRITER

      public static final TreeRewriter<Op<Double>> ARITHMETIC_REWRITER
      This rewriter implements some common arithmetic identities, in exactly this order. 
       
     sub($x,$x) ->  0
     sub($x,0)  ->  $x
     add($x,0)  ->  $x
     add(0,$x)  ->  $x
     add($x,$x) ->  mul(2,$x)
     div($x,$x) ->  1
     div(0,$x)  ->  0
     mul($x,0)  ->  0
     mul(0,$x)  ->  0
     mul($x,1)  ->  $x
     mul(1,$x)  ->  $x
     mul($x,$x) ->  pow($x,2)
     pow($x,0)  ->  1
     pow(0,$x)  ->  0
     pow($x,1)  ->  $x
     pow(1,$x)  ->  1
      Since:
      5.0

    • REWRITER

      public static final TreeRewriter<Op<Double>> REWRITER
      Combination of the ARITHMETIC_REWRITER and the CONST_REWRITER, in this specific order.
      Since:
      5.0

  • Constructor Details

    • MathExpr

      public MathExpr(Tree<? extends Op<Double>,?> tree)
      Create a new MathExpr object from the given operation tree.
      Parameters:
      tree - the underlying operation tree
      Throws:
      NullPointerException - if the given program is null
      IllegalArgumentException - if the given operation tree is invalid, which means there is at least one node where the operation arity and the node child count differ.

  • Method Details

    • vars

      public ISeq<Var<Double>> vars()
      Return the variable list of this math expression.
      Returns:
      the variable list of this math expression

    • tree

      public Tree<Op<Double>,?> tree()
      Return the operation tree underlying this math expression.
      Returns:
      the operation tree s
      Since:
      7.1

    • toTree

      @Deprecated(forRemoval=true) public TreeNode<Op<Double>> toTree()
      Deprecated, for removal: This API element is subject to removal in a future version.
      Will be removed, use tree() instead
      Return the math expression as an operation tree.
      Returns:
      a new expression tree

    • apply

      public Double apply(Double[] args)
      Specified by:
      apply in interface Function<Double[],Double>
      See Also:

    • eval

      public double eval(double... args)
      Convenient method, which lets you apply the program function without explicitly create a wrapper array. 
       final double result = MathExpr.parse("2*z + 3*x - y").eval(3, 2, 1);
 assert result == 9.0;
      Parameters:
      args - the function arguments
      Returns:
      the evaluated value
      Throws:
      NullPointerException - if the given variable array is null
      IllegalArgumentException - if the length of the argument array is smaller than the program arity
      See Also:

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object

    • toString

      public String toString()
      Return the string representation of this MathExpr object. The string returned by this method can be parsed again and will result in the same expression object. 
       final String expr = "5.0 + 6.0*x + sin(x)^34.0 + (1.0 + sin(x*5.0)/4.0) + 6.5";
 final MathExpr tree = MathExpr.parse(expr);
 assert tree.toString().equals(expr);
      Overrides:
      toString in class Object
      Returns:
      the expression string

    • simplify

      public MathExpr simplify(TreeRewriter<Op<Double>> rewriter, int limit)
      Simplifying this expression by applying the given rewriter and the given rewrite limit.
      Parameters:
      rewriter - the rewriter used for simplifying this expression
      limit - the rewrite limit
      Returns:
      a newly created math expression object
      Throws:
      NullPointerException - if the rewriter is null
      IllegalArgumentException - if the limit is smaller than zero

    • simplify

      public MathExpr simplify(TreeRewriter<Op<Double>> rewriter)
      Simplifying this expression by applying the given rewriter.
      Parameters:
      rewriter - the rewriter used for simplifying this expression
      Returns:
      a newly created math expression object
      Throws:
      NullPointerException - if the rewriter is null

    • simplify

      public MathExpr simplify()
      Simplifies this expression by applying the default REWRITER.
      Returns:
      a newly created math expression object

    • format

      public static String format(Tree<? extends Op<Double>,?> tree)
      Return the string representation of the given tree object. The string returned by this method can be parsed again and will result in the same expression object. 
       final String expr = "5.0 + 6.0*x + sin(x)^34.0 + (1.0 + sin(x*5.0)/4.0) + 6.5";
 final MathExpr tree = MathExpr.parse(expr);
 assert MathExpr.format(tree.tree()).equals(expr);
      Parameters:
      tree - the tree object to convert to a string
      Returns:
      a new expression string
      Throws:
      NullPointerException - if the given tree is null
      Since:
      4.3

    • parse

      public static MathExpr parse(String expression)
      Parses the given expression into an AST tree.
      Parameters:
      expression - the expression string
      Returns:
      the tree representation of the given expression
      Throws:
      NullPointerException - if the given expression is null
      IllegalArgumentException - if the given expression is invalid or can't be parsed.

    • parseTree

      public static Tree<Op<Double>,?> parseTree(String expression)
      Parses the given mathematical expression string and returns the mathematical expression tree. The expression may contain all functions defined in MathOp. 
      final Tree<? extends Op<Double>, ?> tree = MathExpr
    .parseTree("5 + 6*x + sin(x)^34 + (1 + sin(x*5)/4)/6");
      The example above will lead to the following tree: 
       
  add
  ├── add
  │   ├── add
  │   │   ├── 5.0
  │   │   └── mul
  │   │       ├── 6.0
  │   │       └── x
  │   └── pow
  │       ├── sin
  │       │   └── x
  │       └── 34.0
  └── div
      ├── add
      │   ├── 1.0
      │   └── div
      │       ├── sin
      │       │   └── mul
      │       │       ├── x
      │       │       └── 5.0
      │       └── 4.0
      └── 6.0
      Parameters:
      expression - the expression string
      Returns:
      the parsed expression tree
      Throws:
      NullPointerException - if the given expression is null
      IllegalArgumentException - if the given expression is invalid or can't be parsed.

    • eval

      public static double eval(String expression, double... args)
      Evaluates the given expression with the given arguments. 
       final double result = MathExpr.eval("2*z + 3*x - y", 3, 2, 1);
 assert result == 9.0;
      Parameters:
      expression - the expression to evaluate
      args - the expression arguments, in alphabetical order
      Returns:
      the evaluation result
      Throws:
      NullPointerException - if the given expression is null
      IllegalArgumentException - if the given operation tree is invalid, which means there is at least one node where the operation arity and the node child count differ.
      See Also:

    • eval

      public static double eval(Tree<? extends Op<Double>,?> expression, double... args)
      Evaluates the given expression with the given arguments.
      Parameters:
      expression - the expression to evaluate
      args - the expression arguments, in alphabetical order
      Returns:
      the evaluation result
      Throws:
      NullPointerException - if the given expression is null
      Since:
      4.4
      See Also:

    • rewrite

      public static int rewrite(TreeNode<Op<Double>> tree, int limit)
      Applies the REWRITER to the given (mutable) tree. The tree rewrite is done in place.
      Parameters:
      tree - the tree to be rewritten
      limit - the maximal number this rewrite rule is applied to the given tree. This guarantees the termination of the rewrite method.
      Returns:
      the number of rewrites applied to the input tree
      Throws:
      NullPointerException - if the given tree is null
      IllegalArgumentException - if the limit is smaller than one
      Since:
      5.0
      See Also:

    • rewrite

      public static int rewrite(TreeNode<Op<Double>> tree)
      Applies the REWRITER to the given (mutable) tree. The tree rewrite is done in place. The limit of the applied rewrites is set unlimited (Integer.MAX_VALUE).
      Parameters:
      tree - the tree to be rewritten
      Returns:
      true if the tree has been changed (rewritten) by this method, false if the tree hasn't been changed
      Throws:
      NullPointerException - if the given tree is null
      Since:
      5.0
      See Also: