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package org.zwobble.couscous.interpreter;
import org.zwobble.couscous.ast.*;
import org.zwobble.couscous.ast.visitors.AssignableExpressionNodeVisitor;
import org.zwobble.couscous.ast.visitors.ExpressionNodeMapper;
import org.zwobble.couscous.interpreter.errors.ConditionMustBeBoolean;
import org.zwobble.couscous.interpreter.errors.InvalidCast;
import org.zwobble.couscous.interpreter.values.*;
import org.zwobble.couscous.values.BooleanValue;
import org.zwobble.couscous.values.IntegerValue;
import java.util.List;
import java.util.stream.Collectors;
public class Evaluator implements ExpressionNodeMapper<InterpreterValue> {
public static InterpreterValue eval(Environment environment, ExpressionNode expression) {
return new Evaluator(environment).eval(expression);
}
public static boolean evalCondition(Environment environment, ExpressionNode expression) {
return new Evaluator(environment).evalCondition(expression);
}
private final Environment environment;
private Evaluator(Environment environment) {
this.environment = environment;
}
public InterpreterValue eval(ExpressionNode expression) {
return expression.accept(this);
}
@Override
public InterpreterValue visit(LiteralNode literal) {
return InterpreterValues.value(literal.getValue());
}
@Override
public InterpreterValue visit(VariableReferenceNode variableReference) {
return environment.get(variableReference.getReferentId());
}
@Override
public InterpreterValue visit(ThisReferenceNode reference) {
InterpreterValue thisValue = environment.getThis().get();
// TODO: add a test for this
InterpreterTypes.checkIsInstance(reference.getType(), thisValue);
return thisValue;
}
@Override
public InterpreterValue visit(AssignmentNode assignment) {
InterpreterValue value = eval(assignment.getValue());
assignment.getTarget().accept(new AssignableExpressionNodeVisitor(){
@Override
public void visit(FieldAccessNode fieldAccess) {
InterpreterValue left = eval(fieldAccess.getLeft());
left.setField(fieldAccess.getFieldName(), value);
}
@Override
public void visit(VariableReferenceNode reference) {
environment.put(reference.getReferentId(), value);
}
});
return value;
}
@Override
public InterpreterValue visit(TernaryConditionalNode ternaryConditional) {
boolean condition = evalCondition(ternaryConditional.getCondition());
ExpressionNode branch = condition ? ternaryConditional.getIfTrue() : ternaryConditional.getIfFalse();
return eval(branch);
}
private boolean evalCondition(ExpressionNode condition) {
InterpreterValue value = eval(condition);
if (!(value instanceof BooleanInterpreterValue)) {
throw new ConditionMustBeBoolean(value);
}
return ((BooleanInterpreterValue)value).getValue();
}
@Override
public InterpreterValue visit(MethodCallNode methodCall) {
List<InterpreterValue> arguments = evalArguments(methodCall.getArguments());
MethodSignature signature = methodCall.signature();
return methodCall.getReceiver().accept(new Receiver.Mapper<InterpreterValue>() {
@Override
public InterpreterValue visit(ExpressionNode receiverExpression) {
InterpreterValue receiver = eval(receiverExpression);
ConcreteType type = receiver.getType();
return type.callMethod(environment, receiver, signature, arguments);
}
@Override
public InterpreterValue visit(TypeName receiver) {
ConcreteType clazz = environment.findClass(receiver);
return clazz.callStaticMethod(environment, signature, arguments);
}
});
}
@Override
public InterpreterValue visit(ConstructorCallNode call) {
ConcreteType clazz = environment.findClass(call.getType());
List<InterpreterValue> arguments = evalArguments(call.getArguments());
return clazz.callConstructor(environment, arguments);
}
@Override
public InterpreterValue visit(OperationNode operation) {
return eval(operation.desugar());
}
@Override
public InterpreterValue visit(FieldAccessNode fieldAccess) {
InterpreterValue left = eval(fieldAccess.getLeft());
return left.getField(fieldAccess.getFieldName());
}
@Override
public InterpreterValue visit(TypeCoercionNode typeCoercion) {
// TODO: check that the type coercion is valid
// TODO: boxing booleans
InterpreterValue value = eval(typeCoercion.getExpression());
if (isIntegerBox(typeCoercion)) {
return BoxedIntegerInterpreterValue.of(((IntegerInterpreterValue)value));
} else if (isIntegerUnbox(typeCoercion)) {
return value.getField("value");
} else {
return value;
}
}
@Override
public InterpreterValue visit(CastNode cast) {
InterpreterValue value = eval(cast.getExpression());
if (!InterpreterTypes.isSubType(cast.getType(), value.getType())) {
throw new InvalidCast(cast.getType(), value.getType().getName());
}
return value;
}
private static boolean isIntegerBox(TypeCoercionNode typeCoercion) {
return typeCoercion.getExpression().getType().equals(IntegerValue.REF) &&
!typeCoercion.getType().equals(IntegerValue.REF);
}
private static boolean isIntegerUnbox(TypeCoercionNode typeCoercion) {
return !typeCoercion.getExpression().getType().equals(IntegerValue.REF) &&
typeCoercion.getType().equals(IntegerValue.REF);
}
private static boolean isBooleanBox(TypeCoercionNode typeCoercion) {
return typeCoercion.getExpression().getType().equals(BooleanValue.REF) &&
!typeCoercion.getType().equals(BooleanValue.REF);
}
private static boolean isBooleanUnbox(TypeCoercionNode typeCoercion) {
return !typeCoercion.getExpression().getType().equals(BooleanValue.REF) &&
typeCoercion.getType().equals(BooleanValue.REF);
}
private List<InterpreterValue> evalArguments(List<? extends ExpressionNode> arguments) {
return arguments.stream()
.map(argument -> eval(argument))
.collect(Collectors.toList());
}
}
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