输入'='上的解析错误

Question

我一直收到这条消息，我做错了什么？

quadrant :: Float -> Float -> Quadrant
quadrant x y
    |x = 0 && y = 0 = Origin
    |x > 0 && y = 0 = X_ Axis_Positive
    |x > 0 && y > 0 = Quadrant_1
    |x = 0 && y > 0 = Y_ Axis_Positive
    |x < 0 && y > 0 = Quadrant_2
    |x < 0 && y = 0 = X_ Axis_Negative
    |x < 0 && y < 0 = Quadrant_3
    |x = 0 && y < 0 = Y_ Axis_Negative
    |x > 0 && y < 0 = Quadrant_4
    |otherwise = error "Program error: Non-Exhaustive guards in function: quadrant"

Answer 1

测试相等性的运算符是==，其中=是语言语法的一部分。