type exp = Zero | Var of string
type env = (string * int) list
The value zero in the definition of eval is not defined. Since eval returns an int, why not replace zero by 0?
Hope that helps!
type exp = Zero | Var of string
type env = (string * int) list
The value zero in the definition of eval is not defined. Since eval returns an int, why not replace zero by 0?
Hope that helps!