Class ConstraintState

java.lang.Object

org.ek9lang.compiler.phase5.flow.ConstraintState

public final class ConstraintState
extends Object

Immutable constraint state mapping variables to their abstract values.

At each program point, a ConstraintState maps each tracked variable to its abstract value. Untracked variables are implicitly TopValue.INSTANCE.

Supports copy-on-write semantics for branch splitting — creating a new state from an existing one is cheap (shallow copy of the internal map).

Constructor Summary

Constructors

Constructor	Description
ConstraintState()	Create an empty constraint state.

Method Summary

Modifier and Type	Method	Description
ConditionResult	evaluateCondition(AbstractValue left, String operator, AbstractValue right)	Evaluate a condition given the current state of two symbols/values.
AbstractValue	get(ISymbol symbol)	Get the abstract value for a symbol.
boolean	isUnreachable()	Check if this state represents an unreachable program point.
static ConstraintState	join(ConstraintState first, ConstraintState second)	Join this state with another at a branch convergence point.
void	markUnreachable()	Mark this state as unreachable (BOTTOM).
void	set(ISymbol symbol, AbstractValue abstractValue)	Set the abstract value for a symbol (mutates this state).
ConstraintState	snapshot()	Create a snapshot (copy) of this state for branch splitting.
String	toString()

Methods inherited from class Object

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

Constructor Details

ConstraintState

public ConstraintState()

Create an empty constraint state.

Method Details

snapshot

public ConstraintState snapshot()

Create a snapshot (copy) of this state for branch splitting.

get

public AbstractValue get(ISymbol symbol)

Get the abstract value for a symbol. Returns TOP if not tracked.

set

public void set(ISymbol symbol,
 AbstractValue abstractValue)

Set the abstract value for a symbol (mutates this state).

markUnreachable

public void markUnreachable()

Mark this state as unreachable (BOTTOM). Used after throw statements or contradictory conditions.

isUnreachable

public boolean isUnreachable()

Check if this state represents an unreachable program point.

join

public static ConstraintState join(ConstraintState first,
 ConstraintState second)

Join this state with another at a branch convergence point.

If either state is unreachable (BOTTOM), the other state is used. Otherwise, for each variable, the joined value is the lattice join of both branch values.

Parameters:

first - the state from the first branch

second - the state from the second branch

Returns:

a new joined state

evaluateCondition

public ConditionResult evaluateCondition(AbstractValue left,
 String operator,
 AbstractValue right)

Evaluate a condition given the current state of two symbols/values.

Parameters:

left - the abstract value of the left operand

operator - the comparison operator

right - the abstract value of the right operand

Returns:

the condition evaluation result

toString

public String toString()

Overrides:

toString in class Object