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mapi : (int -> 'a -> 'b) -> 'a list -> 'b list

SYNOPSIS

Applies a function to every element of a list, supplying the element's index.

DESCRIPTION

mapi f [x0;...;xn] returns [f 0 x0; f 1 x1;...;f n xn]. The function f receives the zero-based index of each element as its first argument.

FAILURE CONDITIONS

Never fails.

EXAMPLE

  # mapi (fun i x -> (i, x)) ["a"; "b"; "c"];;
  val it : (int * string) list = [(0, "a"); (1, "b"); (2, "c")]
  # mapi (fun i x -> x + i) [10; 20; 30];;
  val it : int list = [10; 21; 32]
  # mapi (fun i _ -> i) [5; 5; 5; 5];;
  val it : int list = [0; 1; 2; 3]

SEE ALSO

map, map2.