FlatPred (CZT ZLive 1.6-SNAPSHOT API)

java.lang.Object
- net.sourceforge.czt.animation.eval.flatpred.FlatPred

Direct Known Subclasses:

FlatBinding, FlatBindSel, FlatCard, FlatConst, FlatDiscreteSet, FlatDiv, FlatEquals, FlatEvalSet, FlatFalse, FlatForall, FlatGivenSet, FlatIfThenElse, FlatLessThan, FlatLessThanEquals, FlatMember, FlatMod, FlatMu, FlatMult, FlatNegate, FlatOr, FlatPlus, FlatPowerSet, FlatPredList, FlatProd, FlatRangeSet, FlatRelSet, FlatSetComp, FlatTuple, FlatTupleSel
```
public abstract class FlatPred
extends Object
```
FlatPred is the base class of the flattened predicates used in ZLive. Each flattened predicate can be evaluated in one or more different 'modes' (a mode is defined by a set of input variables and a set of output variables). Each FlatPred provides facilities for choosing a particular mode, given environment information about what input variables are available, and for generating all solutions using that mode. Note that each FlatPred has at most one mode in a given environment. Environments are updated non-destructively.
Design Rationale: The natural representation of the data inside each kind of FlatPred is quite different to the normal CZT AST classes, which means that the standard CZT visitors and utilities would not automatically work on FlatPred classes. However, for backwards compatibility, the FlatPred classes implement the Pred interface, and generate the appropriate children on the fly, so that they seem to be standard Z AST objects. For example, this allows the usual print visitors to display the FlatPred objects.
The mode selection uses a stateless interface, where the chosen mode information is returned in a separate object rather than changing the internal state of the FlatPred. This enables different input environments to be tried and the corresponding modes stored and compared, which gives more flexibility in the searching algorithms that use modes.

Field Summary

Fields
Modifier and Type	Field and Description
`protected ArrayList<net.sourceforge.czt.z.ast.ZName>`	`args_` The list of arguments to this FlatPred.
`protected Mode`	`evalMode_` The mode that will be used during evaluation.
`protected Set<net.sourceforge.czt.z.ast.ZName>`	`freeVars_` Records the free variables used within this predicate.
`protected static String`	`INDENT`
`protected static Logger`	`LOG`
`protected static net.sourceforge.czt.z.util.PrintVisitor`	`printer_` A non-unicode print visitor used for debug and toString messages.
`protected int`	`solutionsReturned_` The number of solutions that have been returned by nextEvaluation().

Constructor Summary

Constructors
Modifier Constructor and Description

protected FlatPred()
Default constructor for subclasses to call.

Constructors
Modifier	Constructor and Description
`protected`	`FlatPred()` Default constructor for subclasses to call.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`<R> R`	`accept(net.sourceforge.czt.util.Visitor<R> visitor)` Calls visitor.visitPred (preferably) or visitor.visitTerm.
`abstract Mode`	`chooseMode(Envir env)` Choose the mode that this predicate could use in this environment.
`Set<net.sourceforge.czt.z.ast.ZName>`	`freeVars()` Returns the free variables that appear in the predicate.
`List<net.sourceforge.czt.z.ast.ZName>`	`getArgs()` Get the list of variables that this predicate directly depends upon.
`Envir`	`getEnvir()` Get the output environment of the evaluation.
`net.sourceforge.czt.z.ast.ZName`	`getLastArg()` Get the variable at the end of getArgs().
`Mode`	`getMode()` Get the mode that has been set for evaluation purposes.
`String`	`indent(String str)` Indents a multi-line string by replacing all newlines by a newline followed by two spaces.
`boolean`	`inferBounds(Bounds bnds)` Infer bounds for any integer variables.
`protected Mode`	`modeAllDefined(Envir env)` A default implementation of chooseMode.
`Mode`	`modeCollection(Envir env)` A default implementation of chooseMode.
`protected Mode`	`modeFunction(Envir env)` A default implementation of chooseMode.
`protected Mode`	`modeOneOutput(Envir env)` A default implementation of chooseMode.
`abstract boolean`	`nextEvaluation()` Generates the next solution that satisfies this predicate.
`protected String`	`printArg(int argNum)` Pretty-prints the name of the i'th argument, via nameString.
`protected String`	`printBinOp(String op)` A toString method for binary operators.
`protected String`	`printLastArg()` Pretty-prints getLastArg()
`static String`	`printName(net.sourceforge.czt.z.ast.ZName name)` Convenience method to convert a ZName into a string.
`protected String`	`printQuant(String quant, String stext, String body, String endQuant)`
`void`	`setMode(Mode mode)` Set the mode that will be used to evaluate this predicate.
`void`	`startEvaluation()`
`String`	`toString()` A default implementation of toString.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - INDENT
```
protected static final String INDENT
```
    See Also:
    
    Constant Field Values
  - LOG
```
protected static final Logger LOG
```
  - freeVars_
```
protected Set<net.sourceforge.czt.z.ast.ZName> freeVars_
```
    Records the free variables used within this predicate. This is calculated and cached by the freeVars() method.
  - evalMode_
```
protected Mode evalMode_
```
    The mode that will be used during evaluation. This is usually set by an explicit call to setMode().
  - args_
```
protected ArrayList<net.sourceforge.czt.z.ast.ZName> args_
```
    The list of arguments to this FlatPred. If the FlatPred corresponds to a function, the output is the last entry in args. Note that it is permissible for args_ to contain the same name more than once. For example, a*a=b gives FlatMult(a,a,b), which has args_=[a,a,b].
  - solutionsReturned_
```
protected int solutionsReturned_
```
    The number of solutions that have been returned by nextEvaluation(). This is -1 before startEvaluation() is called and 0 immediately after it has been called.
  - printer_
```
protected static net.sourceforge.czt.z.util.PrintVisitor printer_
```
    A non-unicode print visitor used for debug and toString messages.
- Constructor Detail
  - FlatPred
```
protected FlatPred()
```
    Default constructor for subclasses to call.
- Method Detail
  - getArgs
```
public List<net.sourceforge.czt.z.ast.ZName> getArgs()
```
    Get the list of variables that this predicate directly depends upon. This usually contains the same variables as the freeVars set, but this list may contain duplicates. This should be treated as a read-only list.
  - getLastArg
```
public net.sourceforge.czt.z.ast.ZName getLastArg()
```
    Get the variable at the end of getArgs(). This is usually the output' of this FlatPred.
  - getMode
```
public Mode getMode()
```
    Get the mode that has been set for evaluation purposes.
  - getEnvir
```
public Envir getEnvir()
```
    Get the output environment of the evaluation.
    
    Returns:
    
    Envir if known, else null.
  - freeVars
```
public Set<net.sourceforge.czt.z.ast.ZName> freeVars()
```
    Returns the free variables that appear in the predicate. The default implementation returns all the variables in args.
  - inferBounds
```
public boolean inferBounds(Bounds bnds)
```
    Infer bounds for any integer variables. This analyzes the possible range of values of each integer variable used by this FlatPred, and reduces the range of values if possible. This is a kind of static analysis commonly used in constraint solvers (bounds consistency). For example, if y already has the range 10..20, then the FlatPred x < y would set the maximum value of x to 19.
    
    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 abstract Mode chooseMode(Envir env)
```
    Choose the mode that this predicate could use in this environment. The result is null if no evaluation is possible. Otherwise, the resulting Mode object contains an updated environment (with any output variables added), plus various estimates about how expensive this predicate will be to execute.
    
    Returns:
    
    The Mode object, with statistics and an updated environment.
  - modeAllDefined
```
protected Mode modeAllDefined(Envir env)
```
    A default implementation of chooseMode. This returns mode IIIIII.. only. That is, all elements in the args list must be defined in env.
  - modeFunction
```
protected Mode modeFunction(Envir env)
```
    A default implementation of chooseMode. This returns modes IIII... and III...O only. That is, all inputs to the function must be defined in env.
  - modeOneOutput
```
protected Mode modeOneOutput(Envir env)
```
    A default implementation of chooseMode. For example, with 3 args, this returns modes III(0.5), OII(1.0), IOI(1.0), IIO(1.0). That is, n-1 args must be defined in env.
  - modeCollection
```
public Mode modeCollection(Envir env)
```
    A default implementation of chooseMode. Useful when the last argument is a collection (tuple/binding) that contains all the other arguments.
  - setMode
```
public void setMode(Mode mode)
```
    Set the mode that will be used to evaluate this predicate.
    
    Parameters:
    
    mode - Must be one of the modes returned previously by chooseMode.
  - startEvaluation
```
public void startEvaluation()
```
  - nextEvaluation
```
public abstract boolean nextEvaluation()
```
    Generates the next solution that satisfies this predicate. This must only be called after startEvaluation().
    
    Returns:
    
    true iff another solution has been found.
  - printName
```
public static String printName(net.sourceforge.czt.z.ast.ZName name)
```
    Convenience method to convert a ZName into a string. (This controls whether we print internal names with Ids or not.)
    
    Returns:
  - printArg
```
protected String printArg(int argNum)
```
    Pretty-prints the name of the i'th argument, via nameString. If argNum < 0, then this just prints '_', which indicates an optional argument that is not present.
  - printLastArg
```
protected String printLastArg()
```
    Pretty-prints getLastArg()
  - toString
```
public String toString()
```
    A default implementation of toString. This returns "FlatXXX(args[0], args[1], ...)".
    
    Overrides:
    
    toString in class Object
  - printBinOp
```
protected String printBinOp(String op)
```
    A toString method for binary operators. For example, binOpString("+") gives "x + y = z", assuming that args_ contains [x,y,z].
  - printQuant
```
protected String printQuant(String quant,
                            String stext,
                            String body,
                            String endQuant)
```
  - indent
```
public String indent(String str)
```
    Indents a multi-line string by replacing all newlines by a newline followed by two spaces.
    
    Parameters:
    
    str - the (possibly multi-line) string to indent
    
    Returns:
    
    same as str, but perhaps with additional spaces
  - accept
```
public <R> R accept(net.sourceforge.czt.util.Visitor<R> visitor)
```
    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).

Class FlatPred

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

INDENT

LOG

freeVars_

evalMode_

args_

solutionsReturned_

printer_

Constructor Detail

FlatPred

Method Detail

getArgs

getLastArg

getMode

getEnvir

freeVars

inferBounds

chooseMode

modeAllDefined

modeFunction

modeOneOutput

modeCollection

setMode

startEvaluation

nextEvaluation

printName

printArg

printLastArg

toString

printBinOp

printQuant

indent

accept