Re: [Caml-list] pattern matching on mapped lists

[John Whitington <john@coherentgraphics.co.uk>]

Hi Nils,

Nils Becker wrote:
> I find this syntax handy
>
>      let [ii; jj] = List.map float_of_int [i; j] in
>      ... do stuff with the floats
>
> because it avoids repeating the function call. The compiler lets this
> pass but warns that the matching is not exhaustive since [] is not
> matched. This actually can't happen if I'm not mistaken. So, is this
> considered good style, or is there a better idiomatic way to do multiple
> assignments? If yes, should this be an enhancement request for the type
> checker?

If the lengths are almost always small, why not just put appropriate 
functions map_pair, map_tuple3, map_tuple4 etc. into your library?

fun map_tuple3 f (x, y, z) = (f x, f y, f z)

let (ii, jj) = map_pair float_of_int (i, j)

Or, even...

let ii, jj = map_pair float (i, j)

...if you really want to save typing.

John

-- 
John Whitington
Director, Coherent Graphics Ltd
http://www.coherentpdf.com/