[Ocaml-lib-devel] ExtLib.findi and ExtArray.findi

[Christian S. <ext...@cs...>]

Hi,

Looking at CVS I see in ExtArray.mli:

  val findi : ('a -> bool) -> 'a array -> int
    (** [findi p a] returns the index of the first element of array [a]
        that satisfies the predicate [p].
        Raise [Not_found] if there is no value that satisfies [p] in the
        array [a].
    *)

and in ExtList.mli:

   val findi : (int -> 'a -> bool) -> 'a list -> (int * 'a)
     (** [findi p e l] returns the first element [ai] of [l] along with its
         index [i] such that [p i ai] is true, or raises [Not_found] if no
         such element has been found. *)

This seems quite inconsistent to me.   IMHO, a library should attempt to
use equivalent type signatures for functions with the same name.  This
does not only make functions easier to remember but it also allows
easier refactoring of code.  For example

    let i = ExtList.findi p coll in ...

should easily be changable to 

    let i = ExtArray.findi p coll in ...

in case that coll is a collection that's first implemented as a list and
then (while tuning performance) is changed to an array.


In the case at hand I would actually advocate to rename ExtList.findi
to ExtLib.index_by since there should also be a 

    val index : 'a -> 'a array -> int

just as String.index, and index_by would simply be the predicated
variant of the standard index function.  ExtArray.findi should still be
available and should be exchangable with ExtList.findi.

What do you think?

Friendly,
Chris

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