Re: what did I do wrong here ?

Thanks everybody,

I see now what I have done wrong.

Next problem making this work with a power function.

Roelof

Matthieu Dubuget [email protected] [ocaml_beginners]
schreef op 14-10-2014 21:18:

let me try to explain the function another way.

It does not work as you explained, but the other way (from
n to 0).

```ocaml

let rec sum = function

| 0 -> 0

| n -> n + sum(n - 1)

```

sum 3 is replaced by

3 + sum 2 which is replaced by

3 + 2 + sum 1 which is replaced by

3 + 2 + 1 + sum 0 whis is replaced by

3 + 2 + 1 + 0

The factorial function you showed is also working this
way.

We can try to go the other way…

```ocaml

let sum n =

(* we hide a func inside *)

let rec embeded_sum step result =

if step = n (* when n is reached *)

then result + n (* finish with the final

result by summing the previous one with n *)

else sum (step + 1) (step + result) in (* else, increment
the

result with step, and go to the next one *)

embeded_sum 0 0 (* start from 0, with the result 0 *)

````

Here are the values of step and result.

step result

0 0

1 0

2 1

3 3

4 6

5 10

...

--

Matthieu Dubuget

Guide d’autodéfense numérique : http://guide.boum.org

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Posted by: Roelof Wobben <[email protected]>
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