Question

Making a ternary logic table, and I would like to make my own function for an operator that I’ll call <=>.

So, for example, I want to do this, but that isn’t right. what’s the correct way to do this?

data Ternary = T | F | M
deriving (Eq,  Show, Ord)

<=> :: Ternary -> Ternary -> Ternary
<=> T F = F
<=> T T = T
<=> T M = M
<=> F F = T
<=> F T = F
<=> F M = M
<=> M F = M
<=> M T = M
<=> M M = T

Answer 1

Just add parentheses around your operator:

(<=>) :: Ternary -> Ternary -> Ternary
(<=>) T F = F
(<=>) T T = T
(<=>) T M = M
(<=>) F F = T
(<=>) F T = F
(<=>) F M = M
(<=>) M F = M
(<=>) M T = M
(<=>) M M = T

This turns it from infix form to prefix form. Alternatively, you can just use infix in the definition:

(<=>) :: Ternary -> Ternary -> Ternary
T <=> F = F
T <=> T = T
T <=> M = M
F <=> F = T
F <=> T = F
F <=> M = M
M <=> F = M
M <=> T = M
M <=> M = T