Question

I have a function sqrt which takes 2 floating point values, tolerance and number and gives out square root of the number within the specified tolerance. I use approximation method to do it.

let rec sqrt_rec approx tol number =
..................;;
let sqrt tol x = sqrt_rec (x/.2.0) tol x;;

I’ve another function map which takes a function and a list and applies the function to all elements of the list.

let rec map f l = 
match l with
[] -> []
| h::t -> f h::map f t;;

Now I’m trying to create another function all_sqrt which basically takes 1 floating point value, 1 floating point list and maps function sqrt to all the elements.

let all_sqrt tol_value ip_list = List.map sqrt tol_value ip_list;;

It is obviously giving me error. I tried making tol_value also a list but it still throws up error.
Error: This function is applied to too many arguments;
maybe you forgot a `;’

I believe i’m doing mapping wrong.

Answer 1

The List module contains

val map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list

which is used like this:

let all_sqrt tol_value ip_list = List.map2 sqrt tol_value ip_list