Standard Library
Below is the API for the OCaml standard library. It's directly copied over from the OCaml Manual, formatted to the Reason syntax and styled accordingly. The API docs are work-in-progress; we'll be polishing these gradually!
If you're targeting JavaScript, the API docs for BuckleScript includes all of below, plus JS-specific APIs.
sig val zero : nativeint val one : nativeint val minus_one : nativeint external neg : nativeint -> nativeint = "%nativeint_neg" external add : nativeint -> nativeint -> nativeint = "%nativeint_add" external sub : nativeint -> nativeint -> nativeint = "%nativeint_sub" external mul : nativeint -> nativeint -> nativeint = "%nativeint_mul" external div : nativeint -> nativeint -> nativeint = "%nativeint_div" external rem : nativeint -> nativeint -> nativeint = "%nativeint_mod" val succ : nativeint -> nativeint val pred : nativeint -> nativeint val abs : nativeint -> nativeint val size : int val max_int : nativeint val min_int : nativeint external logand : nativeint -> nativeint -> nativeint = "%nativeint_and" external logor : nativeint -> nativeint -> nativeint = "%nativeint_or" external logxor : nativeint -> nativeint -> nativeint = "%nativeint_xor" val lognot : nativeint -> nativeint external shift_left : nativeint -> int -> nativeint = "%nativeint_lsl" external shift_right : nativeint -> int -> nativeint = "%nativeint_asr" external shift_right_logical : nativeint -> int -> nativeint = "%nativeint_lsr" external of_int : int -> nativeint = "%nativeint_of_int" external to_int : nativeint -> int = "%nativeint_to_int" external of_float : float -> nativeint = "caml_nativeint_of_float" external to_float : nativeint -> float = "caml_nativeint_to_float" external of_int32 : int32 -> nativeint = "%nativeint_of_int32" external to_int32 : nativeint -> int32 = "%nativeint_to_int32" external of_string : string -> nativeint = "caml_nativeint_of_string" val to_string : nativeint -> string type t = nativeint val compare : Nativeint.t -> Nativeint.t -> int external format : string -> nativeint -> string = "caml_nativeint_format" end