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[Caml-list] @, List.append, and tail recursion
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 Date: 2003-01-31 (21:30) From: Issac Trotts Subject: Re: [Caml-list] @, List.append, and tail recursion
```On Fri, Jan 31, 2003 at 06:05:30PM +0100, Diego Olivier Fernandez Pons wrote:
>     Bonjour,
>
>
> Brian Hurt wrote :
>
> > I'm basically doing sparse vector/matrix stuff, handling
> > (effectively) (colno * value) list for vectors, and (rowno * vector)
> > list for matrix.  And I may be hitting lists long enough to trip the
> > problem.
>
> If you are doing sparse matrix operations and you still hit lists long
> enough to cause a stack overflow, then your matrix must be really
> huge.
>
> If the ordrer of the terms does not matter (or if you can manage with
> the position information you keep in your sparse matrix) then you just
> need to write tail recursive functions, not taking care of the list
> being reversed
>
> let rec rev_map f result = function
>   | [] -> result

This doesn't work on OCaml 3.06:

"This expression has type 'a but is here used with type 'b -> 'a"

let rec rev_map f result = function
| [] -> result
| head :: tail -> rev_map f (f head :: result) tail;;

# map ((+) 3) [] [1;2;3;4;5];;
- : int list = [8; 7; 6; 5; 4]

Issac

[snip]

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