Getting nth element from a list of floats

Question

If I have a list of floats:

let float_list = [1.5,2.5,3.5]

I'm looking to extract a number from this list similar to:

List.nth float_list 2

However what is returned is type float * float and not 3.5. List.nth only seems to return integers from an integer list and I can't seem to find a function in https://caml.inria.fr/pub/docs/manual-ocaml/libref/List.html to return the nth element of any list other than an integer list.

Would anyone be able to help with this?

Answer 1

Your float_list isn't a list of floats, it's a list of float * float * float tuples and it only contains one such tuple. So in addition to not having the type you want, List.nth float_list 2 will actually cause an exception at run time because 2 is not a valid index for that list.

You want [1.5; 2.5; 3.5], which is actually a list of floats. With that list List.nth will work exactly as you want.

Answer 2

List literals in OCaml use ; to separate items. , is used to separate items in tuples. So the type of float_list is actually (float * float * float) list, and it contains only a single element.