Learning Functional Programming in Go

Sum base classes

Here are our base classes:

type Int32 int32type Int64 int64type Float32 float32type IntSlice []int

We can see from our type definitions that we will be able to sum any two of these base types.

Here’s the Int32 implementation of Sum:

func (i Int32) Sum(s Sum) int64 {   it := int64(i)   switch x := s.(type) {   case Int64:      return it + int64(x)   case Int32:      return it + int64(x)   case Float32:      return it + int64(x)   case IntSlice:      sum := int64(0)      for _, num := range x {         sum += int64(num)      }      return it + sum   default:      return 0   }}

Notice that we return zero if the value we are trying to add our Int32 to is not in the accepted list of types.

Another option would be to implement a result type, like Haskell’s Either type. This is a recent Golang ...