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package org.zwobble.couscous.interpreter;
import org.zwobble.couscous.ast.*;
import org.zwobble.couscous.ast.visitors.DynamicNodeMapper;
import org.zwobble.couscous.ast.visitors.DynamicNodeVisitor;
import org.zwobble.couscous.interpreter.errors.ConditionMustBeBoolean;
import org.zwobble.couscous.interpreter.errors.InvalidCast;
import org.zwobble.couscous.interpreter.values.*;
import org.zwobble.couscous.types.ParameterizedType;
import org.zwobble.couscous.types.ScalarType;
import org.zwobble.couscous.types.Type;
import org.zwobble.couscous.types.Types;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.stream.Collectors;
import static org.zwobble.couscous.types.Types.erasure;
import static org.zwobble.couscous.util.Casts.tryCast;
import static org.zwobble.couscous.util.ExtraLists.eagerMap;
import static org.zwobble.couscous.util.ExtraLists.list;
public class Evaluator {
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 static final BiFunction<Node, Evaluator, InterpreterValue> EVAL = DynamicNodeMapper.visitor(Evaluator.class, "visit");
private final Environment environment;
private Evaluator(Environment environment) {
this.environment = environment;
}
public InterpreterValue eval(ExpressionNode expression) {
return EVAL.apply(expression, this);
}
public InterpreterValue visit(LiteralNode literal) {
return InterpreterValues.value(literal.getValue());
}
public InterpreterValue visit(VariableReferenceNode variableReference) {
return environment.get(variableReference.getReferentId());
}
public InterpreterValue visit(ThisReferenceNode reference) {
InterpreterValue thisValue = environment.getThis().get();
// TODO: add a test for this
//InterpreterTypes.checkIsInstance(reference.getType(), thisValue);
return thisValue;
}
public InterpreterValue visit(ArrayNode array) {
return new ArrayInterpreterValue(
array.getElementType(),
eagerMap(array.getElements(), this::eval));
}
public InterpreterValue visit(AssignmentNode assignment) {
InterpreterValue value = eval(assignment.getValue());
AssignableExpressionVisitor.visit.accept(assignment.getTarget(), new AssignableExpressionVisitor() {
@Override
public void visit(FieldAccessNode fieldAccess) {
ReceiverValue left = evalReceiver(fieldAccess.getLeft());
left.setField(fieldAccess.getFieldName(), value);
}
@Override
public void visit(VariableReferenceNode reference) {
environment.put(reference.getReferentId(), value);
}
});
return value;
}
public interface AssignableExpressionVisitor {
BiConsumer<Node, AssignableExpressionVisitor> visit = DynamicNodeVisitor.visitor(AssignableExpressionVisitor.class);
void visit(VariableReferenceNode node);
void visit(FieldAccessNode node);
}
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();
}
public InterpreterValue visit(MethodCallNode methodCall) {
List<InterpreterValue> arguments = evalArguments(methodCall.getArguments());
MethodSignature signature = methodCall.signature();
return evalReceiver(methodCall.getReceiver())
.callMethod(environment, signature.generic(), new Arguments(list(), arguments));
}
public InterpreterValue visit(ConstructorCallNode call) {
StaticReceiverValue clazz = environment.findClass(erasure(call.getType()));
List<InterpreterValue> arguments = evalArguments(call.getArguments());
List<Type> typeParameters = tryCast(ParameterizedType.class, call.getType())
.map(type -> type.getParameters())
.orElse(list());
return clazz.callConstructor(environment, new Arguments(typeParameters, arguments));
}
public InterpreterValue visit(OperationNode operation) {
return eval(operation.desugar());
}
public InterpreterValue visit(FieldAccessNode fieldAccess) {
ReceiverValue left = evalReceiver(fieldAccess.getLeft());
return left.getField(fieldAccess.getFieldName());
}
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;
}
}
public InterpreterValue visit(CastNode cast) {
InterpreterValue value = eval(cast.getExpression());
if (!InterpreterTypes.isSubType(cast.getType(), value.getType())) {
throw new InvalidCast(cast.getType(), value.getType().getType());
}
return value;
}
private static boolean isIntegerBox(TypeCoercionNode typeCoercion) {
return typeCoercion.getExpression().getType().equals(Types.INT) &&
!typeCoercion.getType().equals(Types.INT);
}
private static boolean isIntegerUnbox(TypeCoercionNode typeCoercion) {
return !typeCoercion.getExpression().getType().equals(Types.INT) &&
typeCoercion.getType().equals(Types.INT);
}
private static boolean isBooleanBox(TypeCoercionNode typeCoercion) {
return typeCoercion.getExpression().getType().equals(Types.BOOLEAN) &&
!typeCoercion.getType().equals(Types.BOOLEAN);
}
private static boolean isBooleanUnbox(TypeCoercionNode typeCoercion) {
return !typeCoercion.getExpression().getType().equals(Types.BOOLEAN) &&
typeCoercion.getType().equals(Types.BOOLEAN);
}
private List<InterpreterValue> evalArguments(List<? extends ExpressionNode> arguments) {
return arguments.stream()
.map(argument -> eval(argument))
.collect(Collectors.toList());
}
private ReceiverValue evalReceiver(Receiver receiver) {
return receiver.accept(new Receiver.Mapper<ReceiverValue>() {
@Override
public ReceiverValue visit(ExpressionNode receiver) {
return new InstanceReceiverValue(eval(receiver));
}
@Override
public ReceiverValue visit(ScalarType receiver) {
return environment.findClass(receiver);
}
});
}
}
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