Method EvalFunc

src/org/apache/pig/EvalFunc.java:101–148

()

    };
    
    public EvalFunc() {
        // Resolve concrete type for T of EvalFunc<T>
        // 1. Build map from type param to type for class hierarchy from current class to EvalFunc
        Map<TypeVariable<?>, Type> typesByTypeVariable = new HashMap<TypeVariable<?>, Type>();
        Class<?> cls = getClass();
        Type type = cls.getGenericSuperclass();
        cls = cls.getSuperclass();
        while (EvalFunc.class.isAssignableFrom(cls)) {
            TypeVariable<? extends Class<?>>[] typeParams = cls.getTypeParameters();
            if (type instanceof ParameterizedType) {
                ParameterizedType pType = (ParameterizedType) type;
                Type[] typeArgs = pType.getActualTypeArguments();
                for (int i = 0; i < typeParams.length; i++) {
                    typesByTypeVariable.put(typeParams[i], typeArgs[i]);
                }
            }
            type = cls.getGenericSuperclass();
            cls = cls.getSuperclass();
        }

        // 2. Use type param to type map to determine concrete type of for T of EvalFunc<T>
        Type targetType = EvalFunc.class.getTypeParameters()[0];
        while (targetType != null && targetType instanceof TypeVariable) {
            targetType = typesByTypeVariable.get(targetType);
        }
        if (targetType == null
                || targetType instanceof GenericArrayType
                || targetType instanceof WildcardType) {
            throw new RuntimeException(String.format(
                    "Failed to determine concrete type for type parameter T of EvalFunc<T> for derived class '%s'",
                    getClass().getName()));
        }
        returnType = targetType;

        // Type check the initial, intermediate, and final functions
        if (this instanceof Algebraic){
            Algebraic a = (Algebraic)this;

            String errMsg = "function of " + getClass().getName() + " is not of the expected type.";
            if (getReturnTypeFromSpec(new FuncSpec(a.getInitial())) != Tuple.class)
                throw new RuntimeException("Initial " + errMsg);
            if (getReturnTypeFromSpec(new FuncSpec(a.getIntermed())) != Tuple.class)
                    throw new RuntimeException("Intermediate " + errMsg);
            if (!getReturnTypeFromSpec(new FuncSpec(a.getFinal())).equals(returnType))
                    throw new RuntimeException("Final " + errMsg);
        }

    }


    private Type getReturnTypeFromSpec(FuncSpec funcSpec){