# Module Core_printf

    module Core_printf: sig .. end

###### Formatting error and exit functions

These functions have polymorphic return type, since they do not return. Naively, this doesn't mix well with variadic functions: if you define, say,

          let f fmt = ksprintf (fun s -> failwith s) fmt

then you find that `f "%d" : int -> 'a`, as you'd expect, and `f "%d" 7 : 'a`. The problem with this is that `'a` unifies with (say) `int -> 'b`, so `f "%d" 7 4` is not a type error -- the `4` is simply ignored.

To mitigate this problem, these functions all take a final unit parameter. These rarely arise as formatting positional parameters (they can do with e.g. "%a", but not in a useful way) so they serve as an effective signpost for "end of formatting arguments".

    val fprintf : Pervasives.out_channel ->
           ('r, Pervasives.out_channel, unit) Pervasives.format -> 'r

    val printf : ('r, Pervasives.out_channel, unit) Pervasives.format -> 'r

    val eprintf : ('r, Pervasives.out_channel, unit) Pervasives.format -> 'r

    val ifprintf : 'a -> ('r, 'a, unit) Pervasives.format -> 'r

    val sprintf : ('r, unit, string) Pervasives.format -> 'r

    val bprintf : Buffer.t -> ('r, Buffer.t, unit) Pervasives.format -> 'r

    val kfprintf : (Pervasives.out_channel -> 'a) ->
           Pervasives.out_channel ->
           ('r, Pervasives.out_channel, unit, 'a) Pervasives.format4 -> 'r

    val ksprintf : (string -> 'a) -> ('r, unit, string, 'a) Pervasives.format4 -> 'r

    val kbprintf : (Buffer.t -> 'a) ->
           Buffer.t -> ('r, Buffer.t, unit, 'a) Pervasives.format4 -> 'r

###### Formatting error and exit functions

These functions have polymorphic return type, since they do not return. Naively, this doesn't mix well with variadic functions: if you define, say,

          let f fmt = ksprintf (fun s -> failwith s) fmt

then you find that `f "%d" : int -> 'a`, as you'd expect, and `f "%d" 7 : 'a`. The problem with this is that `'a` unifies with (say) `int -> 'b`, so `f "%d" 7 4` is not a type error -- the `4` is simply ignored.

To mitigate this problem, these functions all take a final unit parameter. These rarely arise as formatting positional parameters (they can do with e.g. "%a", but not in a useful way) so they serve as an effective signpost for "end of formatting arguments".

    val failwithf : ('r, unit, string, unit -> 'a) Pervasives.format4 -> 'r

raises Failure

    val invalid_argf : ('r, unit, string, unit -> 'a) Pervasives.format4 -> 'r

raises Invalid_arg

    val exitf : ('r, unit, string, unit -> 'a) Pervasives.format4 -> 'r

print to stderr; exit 1