@Override
public Value binary(Term.BinaryOperator operator, Term left, Term right) {
Value leftValue = left.accept(this);
Value rightValue = right.accept(this);
double l = leftValue.accept(extractNumber);
double r = rightValue.accept(extractNumber);
switch (operator) {
case add:
return values.number(l + r);
case sub:
return values.number(l - r);
case mult:
return values.number(l * r);
case div:
return values.number(l / r);
default:
throw new RuntimeException("Unknown operator: " + operator);
}
}
@Override
public Value match(final String typeName, final Map<String, Term.Case> cases, Term term) {
Value value = term.accept(this);
return value.accept(
new Value.Visitor<Value>() {
@Override
public Value number(double value) {
throw new RuntimeException("Expected sum type");
}
@Override
public Value record(String typeName, Map<String, Value> fields) {
throw new RuntimeException("Expected sum type");
}
@Override
public Value constructor(String sumTypeName, String constructorName, Value value) {
if (!sumTypeName.equals(typeName)) {
throw new RuntimeException(
"Wrong sum type constructor (found "
+ sumTypeName
+ " but expected "
+ typeName
+ ")");
}
Term.Case target = cases.get(constructorName);
if (target == null) {
throw new RuntimeException("No such constructor: " + constructorName);
}
if (target.variableName != null) {
Value oldValue = environment.get(target.variableName);
Value result = target.body.accept(Evaluator.this);
environment.put(target.variableName, oldValue);
return result;
} else {
return target.body.accept(Evaluator.this);
}
}
});
}