Package edu.udel.cis.vsl.sarl.simplify.simplifier

Class SubContext

java.lang.Object

edu.udel.cis.vsl.sarl.simplify.simplifier.Context

edu.udel.cis.vsl.sarl.simplify.simplifier.SubContext

All Implemented Interfaces:

ContextIF

public class SubContext
extends Context

A sub-context represents a boolean expression that holds within the context of some other assumption. Hence everything in the super-context is assumed to hold, in addition to everything in the sub-context. This is used to provide scoping to contexts.

Field Summary

Fields

Modifier and Type	Field	Description
static boolean	debug	Should we print debugging information?
static final PrintStream	out	Where the debugging output goes.

Constructor Summary

Constructors

Constructor	Description
SubContext(Context superContext, Set<SymbolicExpression> simplificationStack)	New empty sub-context (equivalent to assumption true).
SubContext(Context superContext, Set<SymbolicExpression> simplificationStack, BooleanExpression assumption)	Creates new sub-context and initializes it using the given assumption.

Method Summary

Modifier and Type	Method	Description
Context	getGlobalContext()
LinearSolver	getLinearSolver()	Constructs an instance of LinearSolver that can be used to simplify the Context.subMap of this Context.
SymbolicExpression	getSub(SymbolicExpression key)	Looks up an entry in the substitution map of this context.
SymbolicExpression	simplify(SymbolicExpression expr)	Simplifies a symbolic expression using the current state of this Context.

Methods inherited from class edu.udel.cis.vsl.sarl.simplify.simplifier.Context

addSub, assume, cacheSimplification, clearSimplifications, clone, computeRange, getFullAssumption, getInfo, getRangeMap, getReducedAssumption, getSimplification, getSubEntries, isInconsistent, normalize, print, putSub, removeSubkey, restrictRange, standardizePair, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

debug

public static boolean debug

Should we print debugging information?

out

public static final PrintStream out

Where the debugging output goes.

Constructor Details

SubContext

public SubContext(Context superContext,
 Set<SymbolicExpression> simplificationStack)

New empty sub-context (equivalent to assumption true).

Parameters:

superContext - the (non-null) context containing this one

simplificationStack - the symbolic expressions that have already been seen; used to prevent cycles (currently only in debug mode)

SubContext

public SubContext(Context superContext,
 Set<SymbolicExpression> simplificationStack,
 BooleanExpression assumption)

Creates new sub-context and initializes it using the given assumption.

Parameters:

superContext - the (non-null) context containing this one

simplificationStack - the symbolic expressions that have already been seen; used to prevent cycles (currently only in debug mode)

assumption - the boolean expression to be represented by this sub-context

Method Details

getSub

public SymbolicExpression getSub(SymbolicExpression key)

Looks up an entry in the substitution map of this context. This method is overridden in the SubContext class.

Looks first in this sub-context for an entry in the sub map for the given key. If none is found, then looks in the super-context.

Overrides:

getSub in class Context

Parameters:

key - the key to look up

Returns:

the simplified expression that should replace key, or null

getLinearSolver

public LinearSolver getLinearSolver()

Constructs an instance of LinearSolver that can be used to simplify the Context.subMap of this Context.

For this sub-context, a form of "relative" Gaussian elimination is performed. The linear equalities of this sub-context are simplified using the information from the super-context before ordinary Gaussian elimination is performed.

Overrides:

getLinearSolver in class Context

Returns:

a linear solver based on relative Gaussian elimination that can be used to simplify the substitution map of this sub-context assuming all substitutions in the super context

simplify

public SymbolicExpression simplify(SymbolicExpression expr)

Description copied from class: Context

Simplifies a symbolic expression using the current state of this Context.

Overrides:

simplify in class Context

Parameters:

expr - the expression to simplify

Returns:

the simplified expression

getGlobalContext

public Context getGlobalContext()

Overrides:

getGlobalContext in class Context