net.sourceforge.czt.animation.eval.flatpred

Class FlatIfThenElse

java.lang.Object

net.sourceforge.czt.animation.eval.flatpred.FlatPred

net.sourceforge.czt.animation.eval.flatpred.FlatIfThenElse

public class FlatIfThenElse
extends FlatPred

FlatIfThenElse(p, e1,n1, e2,n2, resultName) implements (p => n1=e1 and resultName=n1) and (not(p) => n2=e2 and resultName=n2) It requires all free vars of p, e1 and e2 to be ground. This IF-THEN-ELSE uses three separate FlatPredLists (for p, e1, e2). Given an input environment env0, it evaluates all of those FlatPredLists using env0, and then extends env0 by binding just resultName to the result of e1 (if p is true) or e2 (if p is false). This implementation of IF-THEN-ELSE is quite similar to FlatOr, but here the two expressions cannot return multiple solutions, whereas in FlatOr each predicate may have any number of solutions.

Author:

marku

Field Summary

Fields

Modifier and Type	Field and Description
protected FlatPredList	left_ The left-hand expr.
protected Bounds	leftBounds_ Bounds information for the left_ expression.
protected net.sourceforge.czt.z.ast.ZName	leftResult_ The name that left_ binds its value to.
protected FlatPredList	pred_ The predicate that controls the choice.
protected FlatPredList	right_ The right-hand expr, once known.
protected Bounds	rightBounds_ Bounds information for the right_ expression.
protected net.sourceforge.czt.z.ast.ZName	rightResult_ The name that right_ binds its value to.
protected net.sourceforge.czt.z.ast.ZName	wholeResult_ The name that the result of the whole IF-THEN-ELSE is bound to.

Fields inherited from class net.sourceforge.czt.animation.eval.flatpred.FlatPred

args_, evalMode_, freeVars_, INDENT, LOG, printer_, solutionsReturned_

Constructor Summary

Constructors

Constructor and Description
FlatIfThenElse(FlatPredList pred, FlatPredList left, net.sourceforge.czt.z.ast.ZName leftResult, FlatPredList right, net.sourceforge.czt.z.ast.ZName rightResult, net.sourceforge.czt.z.ast.ZName wholeResult) Creates a new instance of FlatUnion.

Method Summary

Modifier and Type	Method and Description
<R> R	accept(net.sourceforge.czt.util.Visitor<R> visitor) Calls visitor.visitPred (preferably) or visitor.visitTerm.
Mode	chooseMode(Envir env0) This requires pred_ and both of left_ and right_ expressions to have valid modes, because in general, we may have to evaluate both expressions.
boolean	inferBounds(Bounds bnds) Bounds information flows into pred_, left_ and right_, but not out.
boolean	nextEvaluation() Generates the next solution that satisfies this predicate.
void	setMode(Mode mode) Set the mode that will be used to evaluate this list.
String	toString() A default implementation of toString.

Methods inherited from class net.sourceforge.czt.animation.eval.flatpred.FlatPred

freeVars, getArgs, getEnvir, getLastArg, getMode, indent, modeAllDefined, modeCollection, modeFunction, modeOneOutput, printArg, printBinOp, printLastArg, printName, printQuant, startEvaluation

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

pred_

protected FlatPredList pred_

The predicate that controls the choice.

left_

protected FlatPredList left_

The left-hand expr.

leftResult_

protected net.sourceforge.czt.z.ast.ZName leftResult_

The name that left_ binds its value to.

leftBounds_

protected Bounds leftBounds_

Bounds information for the left_ expression.

right_

protected FlatPredList right_

The right-hand expr, once known.

rightResult_

protected net.sourceforge.czt.z.ast.ZName rightResult_

The name that right_ binds its value to.

rightBounds_

protected Bounds rightBounds_

Bounds information for the right_ expression.

wholeResult_

protected net.sourceforge.czt.z.ast.ZName wholeResult_

The name that the result of the whole IF-THEN-ELSE is bound to.

Constructor Detail

FlatIfThenElse

public FlatIfThenElse(FlatPredList pred,
                      FlatPredList left,
                      net.sourceforge.czt.z.ast.ZName leftResult,
                      FlatPredList right,
                      net.sourceforge.czt.z.ast.ZName rightResult,
                      net.sourceforge.czt.z.ast.ZName wholeResult)

Creates a new instance of FlatUnion.

Method Detail

inferBounds

public boolean inferBounds(Bounds bnds)

Bounds information flows into pred_, left_ and right_, but not out.

Overrides:

inferBounds in class FlatPred

Parameters:

bnds - The database of lower and upper bounds for integer variables.

Returns:

true iff the bnds database has been changed.

The default implementation infers nothing and returns false.

chooseMode

public Mode chooseMode(Envir env0)

This requires pred_ and both of left_ and right_ expressions to have valid modes, because in general, we may have to evaluate both expressions. For example {x:0..y @ IF x<5 THEN 0 ELSE 10} (depending on y, this may use only the THEN expression, or both).

Specified by:

chooseMode in class FlatPred

Returns:

The Mode object, with statistics and an updated environment.

setMode

public void setMode(Mode mode)

Set the mode that will be used to evaluate this list.

Overrides:

setMode in class FlatPred

Parameters:

mode - Must be one of the modes returned previously by chooseMode.

nextEvaluation

public boolean nextEvaluation()

Description copied from class: FlatPred

Generates the next solution that satisfies this predicate. This must only be called after startEvaluation().

Specified by:

nextEvaluation in class FlatPred

Returns:

true iff another solution has been found.

toString

public String toString()

Description copied from class: FlatPred

A default implementation of toString. This returns "FlatXXX(args[0], args[1], ...)".

Overrides:

toString in class FlatPred

accept

public <R> R accept(net.sourceforge.czt.util.Visitor<R> visitor)

Description copied from class: FlatPred

Calls visitor.visitPred (preferably) or visitor.visitTerm. Subclasses that correspond to particular kinds of Pred should override this to call more specific visitXXX methods (and should call super to handle the remaining cases).

Overrides:

accept in class FlatPred