blog
Class TrueFormula

java.lang.Object
  extended by blog.ArgSpec
      extended by blog.Formula
          extended by blog.TrueFormula

public class TrueFormula
extends Formula

A Formula consisting of just the zero-ary logical operator "true", which is true in every world under every assignment.


Field Summary
static TrueFormula TRUE
          A canonical instance of TrueFormula.
 
Fields inherited from class blog.Formula
ALL_OBJECTS, NOT_EXPLICIT
 
Fields inherited from class blog.ArgSpec
location
 
Constructor Summary
TrueFormula()
          Creates a new TrueFormula.
 
Method Summary
 boolean checkTypesAndScope(Model model, java.util.Map scope)
          Returns true if, within the given scope, all the variables used in this ArgSpec are in scope and all type constraints are satisfied.
 boolean equals(java.lang.Object o)
          Any two instances of TrueFormula are equal.
 java.lang.Object evaluate(EvalContext context)
          Returns the value of this argument specification in the given context.
protected  Formula getEquivToNegationInternal()
          A formula equivalent to the negation of "true" is the empty disjunction, which is always false.
 java.util.Set getNonSatisfiersIfExplicit(EvalContext context, LogicalVar subject, GenericObject genericObj)
          Returns the set of values for the logical variable subject that are consistent with the generating function values of genericObj and that make this formula false in the given context, if this set can be determined without enumerating possible values for subject.
 ConjFormula getPropCNF()
          The CNF form of TrueFormula has no conjuncts.
 DisjFormula getPropDNF()
          The DNF form of TrueFormula has just one disjunct, which is an empty conjunction.
 java.util.Set getSatisfiersIfExplicit(EvalContext context, LogicalVar subject, GenericObject genericObj)
          Returns the set of values for the logical variable subject that are consistent with the generating function values of genericObj and that make this formula true in the given context, if this set can be determined without enumerating possible values for subject.
 Formula getStandardForm()
          The standard form of the formula "true" is an empty conjunction, which is always true.
 ArgSpec getSubstResult(Substitution subst, java.util.Set<LogicalVar> boundVars)
          Returns the result of applying the substitution subst to this expression, excluding the logical variables in boundVars.
 int hashCode()
           
 java.lang.String toString()
          Returns the string "true".
 
Methods inherited from class blog.Formula
compile, containsAnyTerm, containsRandomSymbol, containsTerm, getEquivToNegation, getGenFuncsApplied, getSubExprs, getSubformulas, getTopLevelTerms, isElementary, isLiteral, isQuantified, isTrue
 
Methods inherited from class blog.ArgSpec
evaluate, evaluate, getFreeVars, getLocation, getSubstResult, getValueIfNonRandom, getVariable, isDetermined, isNumeric, setLocation
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

TRUE

public static final TrueFormula TRUE
A canonical instance of TrueFormula.

Constructor Detail

TrueFormula

public TrueFormula()
Creates a new TrueFormula.

Method Detail

evaluate

public java.lang.Object evaluate(EvalContext context)
Description copied from class: ArgSpec
Returns the value of this argument specification in the given context. Returns null if the partial world in this context is not complete enough to evaluate this ArgSpec, or if this ArgSpec contains a free variable that is not assigned a value in the given context.

Specified by:
evaluate in class ArgSpec

getStandardForm

public Formula getStandardForm()
The standard form of the formula "true" is an empty conjunction, which is always true.

Overrides:
getStandardForm in class Formula

getEquivToNegationInternal

protected Formula getEquivToNegationInternal()
A formula equivalent to the negation of "true" is the empty disjunction, which is always false.

Overrides:
getEquivToNegationInternal in class Formula

getPropCNF

public ConjFormula getPropCNF()
The CNF form of TrueFormula has no conjuncts.

Overrides:
getPropCNF in class Formula

getPropDNF

public DisjFormula getPropDNF()
The DNF form of TrueFormula has just one disjunct, which is an empty conjunction.

Overrides:
getPropDNF in class Formula

getSatisfiersIfExplicit

public java.util.Set getSatisfiersIfExplicit(EvalContext context,
                                             LogicalVar subject,
                                             GenericObject genericObj)
Description copied from class: Formula
Returns the set of values for the logical variable subject that are consistent with the generating function values of genericObj and that make this formula true in the given context, if this set can be determined without enumerating possible values for subject. Returns the special value Formula.NOT_EXPLICIT if determining the desired set would requiring enumerating possible values for subject. Also, returns the special value Formula.ALL_OBJECTS if this formula is true in the given context for all objects consistent with genericObj. Finally, returns null if it tries to access an uninstantiated random variable.

Specified by:
getSatisfiersIfExplicit in class Formula
Parameters:
context - an evaluation context that does not assign a value to the logical variable subject
subject - a logical variable
genericObj - a GenericObject instance, which can stand for any object of a given type or include values for certain generating functions

getNonSatisfiersIfExplicit

public java.util.Set getNonSatisfiersIfExplicit(EvalContext context,
                                                LogicalVar subject,
                                                GenericObject genericObj)
Description copied from class: Formula
Returns the set of values for the logical variable subject that are consistent with the generating function values of genericObj and that make this formula false in the given context, if this set can be determined without enumerating possible values for subject. Returns the special value Formula.NOT_EXPLICIT if determining the desired set would requiring enumerating possible values for subject. Also, returns the special value Formula.ALL_OBJECTS if this formula is false in the given context for all objects consistent with genericObj. Finally, returns null if it tries to access an uninstantiated random variable.

This default implementation calls getEquivToNegation, then calls getSatisfiersIfExplicit on the resulting formula. Warning: subclasses must override either this method or getEquivToNegationInternal to avoid an UnsupportedOperationException.

Overrides:
getNonSatisfiersIfExplicit in class Formula
Parameters:
context - an evaluation context that does not assign a value to the logical variable subject
subject - a logical variable
genericObj - a GenericObject instance, which can stand for any object of a given type or include values for certain generating functions

equals

public boolean equals(java.lang.Object o)
Any two instances of TrueFormula are equal.

Overrides:
equals in class java.lang.Object

hashCode

public int hashCode()
Overrides:
hashCode in class java.lang.Object

toString

public java.lang.String toString()
Returns the string "true".

Overrides:
toString in class java.lang.Object

checkTypesAndScope

public boolean checkTypesAndScope(Model model,
                                  java.util.Map scope)
Description copied from class: ArgSpec
Returns true if, within the given scope, all the variables used in this ArgSpec are in scope and all type constraints are satisfied. If there is a type or scope error, prints an appropriate message to standard error and returns false.

Specified by:
checkTypesAndScope in class ArgSpec
scope - a Map from variable names (Strings) to LogicalVar objects

getSubstResult

public ArgSpec getSubstResult(Substitution subst,
                              java.util.Set<LogicalVar> boundVars)
Description copied from class: ArgSpec
Returns the result of applying the substitution subst to this expression, excluding the logical variables in boundVars. This method is used for recursive calls. The set boundVars should contain those variables that are bound in the syntax tree between this sub-expression and the top-level expression to which the substitution is being applied.

Specified by:
getSubstResult in class ArgSpec