How can go-lang curry? - functional-programming

Question

In functional programming likes Haskell, I can define function
add a b = a+b
Then add 3 will return a function that take one parameter and will return 3 + something
How can I do this in GO?
When I define a function that take more than one (say n) parameters, can I only give it one parameter and get another function that take n-1 parameters?
Update:
Sorry for the imprecise words in my original question.
I think my question should be asked as two qeustions:
Is there partial application in GO?
How GO do function curry?
Thanks TheOnly92 and Alex for solving my second question. However, I am also curious about the first question.

Answer 1

To extend on the previous answer, which allows you to take an arbitrary number of arguments:
package main
import (
"fmt"
)
func mkAdd(a int) func(...int) int {
return func(b... int) int {
for _, i := range b {
a += i
}
return a
}
}
func main() {
add2 := mkAdd(2)
add3 := mkAdd(3)
fmt.Println(add2(5,3), add3(6))
}

Answer 2

Perhaps something like
package main
import (
"fmt"
)
func mkAdd(a int) func(int) int {
return func(b int) int {
return a + b
}
}
func main() {
add2 := mkAdd(2)
add3 := mkAdd(3)
fmt.Println(add2(5), add3(6))
}

Answer 3

You can take it a step further by defining a function type and then adding a method to it.
package main
import "fmt"
type Add func(int, int) int
func (f Add) Apply(i int) func(int) int {
return func(j int) int {
return f(i, j)
}
}
func main() {
var add Add = func(i, j int) int { return i + j }
add3 := add.Apply(3)
fmt.Println("add 3 to 2:", add3(2))
}
You can even try with variadic functions:
package main
import "fmt"
type Multiply func(...int) int
func (f Multiply) Apply(i int) func(...int) int {
return func(values ...int) int {
values = append([]int{i}, values...)
return f(values...)
}
}
func main() {
var multiply Multiply = func(values ...int) int {
var total int = 1
for _, value := range values {
total *= value
}
return total
}
var times2 Multiply = multiply.Apply(2)
fmt.Println("times 2:", times2(3, 4), "(expect 24)")
// ... and you can even cascade (if assigned the Multiply type)
times6 := times2.Apply(3)
fmt.Println("times 6:", times6(2, 3, 5, 10), "(expect 1800)")
}
Hope this helps!