Class Expression

java.lang.Object
com.blackrook.expression.Expression
public class Expression extends Object
An expression object for evaluating dynamic calculations. Expressions, at best, should do no memory allocations during evaluation - they can be called multiple times per gametic.
Author:
Matthew Tropiano

  • Field Details

    • RETURN_VARIABLE

      public static final String RETURN_VARIABLE
      Return variable name.
      See Also:

    • TRUE

      public static final Expression TRUE
      Expression: literal true.

    • FALSE

      public static final Expression FALSE
      Expression: literal false.

    • FLOAT_0

      public static final Expression FLOAT_0
      Expression: literal 0.0.

    • FLOAT_1

      public static final Expression FLOAT_1
      Expression: literal 1.0.

    • INTEGER_0

      public static final Expression INTEGER_0
      Expression: literal 0.

    • INTEGER_1

      public static final Expression INTEGER_1
      Expression: literal 1.

    • INFINITY

      public static final Expression INFINITY
      Expression: Infinity.

    • NAN

      public static final Expression NAN
      Expression: NaN.

  • Method Details

    • create

      public static Expression create(boolean value)
      Creates an expression that is just one value.
      Parameters:
      value - the value.
      Returns:
      a new expression.

    • create

      public static Expression create(long value)
      Creates an expression that is just one value.
      Parameters:
      value - the value.
      Returns:
      a new expression.

    • create

      public static Expression create(double value)
      Creates an expression that is just one value.
      Parameters:
      value - the value.
      Returns:
      a new expression.

    • create

      public static Expression create(ExpressionValue value)
      Creates an expression that is just one value.
      Parameters:
      value - the value.
      Returns:
      a new expression.

    • create

      public static Expression create(ExpressionNode[] nodes)
      Creates an expression that is a full expression.
      Parameters:
      nodes - the list of expression nodes.
      Returns:
      a new expression.

    • evaluate

      public void evaluate(ExpressionStack stack, ExpressionVariableContext context, ExpressionValue out)
      Evaluates this expression.
      Parameters:
      stack - the expression stack to use.
      context - the mutable variable context to use.
      out - the output value (returned value, top of stack, or literal value encapsulated).

    • evaluate

      public void evaluate(ExpressionVariableContext context, ExpressionValue out)
      Evaluates this expression. Creates a new stack.
      Parameters:
      context - the mutable variable context to use.
      out - the output value (returned value, top of stack, or literal value encapsulated).

    • evaluate

      public void evaluate(ExpressionValue out)
      Evaluates this expression. Creates a new stack, and an empty context.
      Parameters:
      out - the output value (returned value, top of stack, or literal value encapsulated).

    • evaluate

      public ExpressionValue evaluate()
      Evaluates this expression. Creates a new stack, an empty context, and a value to put the result in.
      Returns:
      the output value (returned value, top of stack, or literal value encapsulated).

    • collapse

      public void collapse()
      Collapses this expression.
      See Also:

    • isCollapsible

      public boolean isCollapsible()
      Checks if this expression is collapsable.
      Returns:
      true if so, false if not.

    • isValue

      public boolean isValue()
      Checks if this is just a literal value (not complex).
      Returns:
      true if so, false if not.

    • getSource

      public String getSource()
      Gets the source code that was used to create this expression.
      Returns:
      the source or null if not created from a string.

    • getDigest

      public String getDigest()
      Gets the SHA-1 digest of this expression, in order to find duplicates. Within the Universe of all expressions, this digest should be sufficient enough to find equal expressions. Under the covers, this calculates the digest if it hasn't been calculated, yet. If it has, it returns the previously calculated digest.
      Returns:
      the SHA-1 digest.

    • getDigest

      public String getDigest(boolean forceRecalc)
      Gets the SHA1 digest of this expression, in order to find duplicates.
      Parameters:
      forceRecalc - if true, forces a recalculation before return.
      Returns:
      a byte array of the digest.
      Throws:
      ExpressionException - if the digest could not be calculated for some reason.

    • intern

      public Expression intern()
      Internalizes an expression: adds this expression to an internal bank and returns it, or returns an existing reference for the same expression already stored.
      Returns:
      this expression, or a reference to an equal one.

    • equals

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

    • equals

      public boolean equals(Expression other)
      Tests if two expressions are the same. Only checks the digests - SHA1 hashes should be good enough.
      Parameters:
      other - the other expression.
      Returns:
      true if so, false if not.

    • toString

      public String toString()
      Overrides:
      toString in class Object