com.singularsys.jep.functions
Class If
java.lang.Object
com.singularsys.jep.functions.PostfixMathCommand
com.singularsys.jep.functions.If
- All Implemented Interfaces:
- CallbackEvaluationI, PostfixMathCommandI, java.io.Serializable
public class If
- extends PostfixMathCommand
- implements CallbackEvaluationI
The if(condExpr, posExpr, negExpr) function.
The value of trueExpr will be returned if condExpr is >0 or Boolean.TRUE
and value of negExpr will be returned if condExpr is <= 0 or Boolean.TRUE.
If condExpr is NaN then NaN is returned.
This function performs lazy evaluation so that
only posExpr or negExpr will be evaluated.
For Complex numbers only the real part is used.
An alternate form if(condExpr, posExpr, negExpr, zeroExpr)
is also available. Note most computations
are carried out over floating point doubles so
testing for zero can be dangerous.
This function implements the SpecialEvaluationI interface
so that it handles setting the value of a variable.
- Since:
- Feb 05 Handles Number arguments, so works with Integers rather than just Doubles
- Version:
- 2.3.0 beta 1 now supports a Boolean first argument.
- Author:
- Rich Morris
Created on 18-Nov-2003
- See Also:
- Serialized Form
Constructor Summary |
If()
|
If(java.lang.Object falseValue)
|
Method Summary |
boolean |
checkNumberOfParameters(int n)
Checks the number of parameters of the call. |
java.lang.Object |
evaluate(Node node,
Evaluator pv)
Performs some special evaluation on the node. |
void |
run(java.util.Stack<java.lang.Object> aStack)
Run the function on the stack. |
Methods inherited from class com.singularsys.jep.functions.PostfixMathCommand |
asArray, asBool, asDouble, asInt, asLong, asStrictInt, asString, checkStack, getName, getNumberOfParameters, setCurNumberOfParameters, setName, toString |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
If
public If()
If
public If(java.lang.Object falseValue)
- Parameters:
falseValue
-
checkNumberOfParameters
public boolean checkNumberOfParameters(int n)
- Checks the number of parameters of the call.
- Specified by:
checkNumberOfParameters
in interface PostfixMathCommandI
- Overrides:
checkNumberOfParameters
in class PostfixMathCommand
- Parameters:
n
- number of parameters function will be called with.
- Returns:
- false if an illegal number of parameters is supplied, true otherwise.
evaluate
public java.lang.Object evaluate(Node node,
Evaluator pv)
throws EvaluationException
- Description copied from interface:
CallbackEvaluationI
- Performs some special evaluation on the node.
This method has the responsibility for evaluating the children of the node
and it should generally call
pv.eval(node.jjtGetChild(i))
for each child.
The SymbolTable is not passed as an argument. This is because
it is better practice to get and set variable values by using
node.getVar().setValue() rather that through the SymbolTable with
requires a hashtable lookup.
- Specified by:
evaluate
in interface CallbackEvaluationI
- Parameters:
node
- The current nodepv
- The visitor, can be used evaluate the children
- Returns:
- the value after evaluation
- Throws:
EvaluationException
- See Also:
Evaluator
run
public void run(java.util.Stack<java.lang.Object> aStack)
throws EvaluationException
- Description copied from interface:
PostfixMathCommandI
- Run the function on the stack. Pops the arguments from the stack, and
pushes the result on the top of the stack.
- Specified by:
run
in interface PostfixMathCommandI
- Throws:
EvaluationException
Copyright © 2008 Singular Systems http://www.singularsys.com/jep