| java.lang.Object
 edu.hws.jcm.data.ConditionalExpression
| ConditionalExpression | | public class ConditionalExpression implements ExpressionCommand(Code) | | A "conditional expression" is an expression using the "?" operator, such as "(x > 0)? x : -x"
or "x <> 3 ? 1 / (x - 3)". Note that the second case, which follows the ":", is optional.
If not present, the expression has the value Double.NaN when the boolean condition evaluates
to false. A ConditionalExpression object is generated by a parser when it encounters a
"?" operator in the string it is parsing (provided the BOOLEANS option is turned on in that parser).
A ConditionalExpression object holds the two expressions that are the cases in a conditional expression.
Note that the boolean condition is NOT stored in the ConditionalExpression object; it is part of
the ExpressionProgram for the expression in which the conditional expression occurs.
A ConditionalExpression is an ExpressionCommand, meaning that it can occur in an ExpressionProgram.
When the apply() method in this class is called, the boolean condition has already been evaluated,
and the result is on the top of the stack. The ConditionalExpression will look at this result
and replace it with the value of one of the two expressions that it contains.
It is unlikely that there will be any reason for anyone to use or understand this class,
except possibly as an example of an ExpressionCommand.
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| ConditionalExpression | | public ConditionalExpression(ExpressionProgram trueCase, ExpressionProgram falseCase)(Code) | | Create a ConditionalExpression object containing the two given expressions.
trueCase must not be null, but falseCase can be null.
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| appendOutputString | | public void appendOutputString(ExpressionProgram prog, int myIndex, StringBuffer buffer)(Code) | | Append the string representation of the expression (including the boolean
condition) to the buffer. Assume that this ConditionalExpression occurs as
a command in prog at index myIndex (so the boolean condition starts at index myIndex-1).
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| apply | | public void apply(StackOfDouble stack, Cases cases)(Code) | | Apply this ConditionalExpression to the stack.
(Get the top item from the stack. If it is non-zero (representing a boolean
value of true), evaluate trueCase and put it's value on the stack. Otherwise,
evaluate falseCase and put its value on the stack. If cases is non-null, record
case values for the boolean condition and for the expression that is evaluated.)
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| compileDerivative | | public void compileDerivative(ExpressionProgram prog, int myIndex, ExpressionProgram deriv, Variable wrt)(Code) | | Add commands to deriv that evaluate the derivative of this conditional expression with
respect to the variable wrt. Assume that the ConditionalExpression Object
occurs in the program prog at index myIndex.
(The derivative of a conditional expression is another conditional expression.
The boolean test for the derivative is the same as the test for this expression,
so copy that test onto deriv. Than add a new ConditionalExpression object to deriv
whose trueCase is the derivative of this.trueCase and whose falseCase is the derivative of
this.falseCase.)
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| dependsOn | | public boolean dependsOn(Variable x)(Code) | | Returns true if x occurs in either the trueCase or the falseCase expression.
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| extent | | public int extent(ExpressionProgram prog, int myIndex)(Code) | | Assume that this ConditionalExpression object occurs in prog at index myIndex.
Compute the total number of commands in prog used by the conditional expression,
including the boolean test, which occurs in prog at position myIndex-1.
(The number of commands in prog used by the conditional expression is 1 (for the
ConditionalExpression object itself) plus the number of commands in the
boolean condition.)
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