Re: pattern matching with keyword function

On 08.04.2016 12:36, cedlemo [email protected] [ocaml_beginners] wrote:
>  
>
> > In pattern matching, the first vertical bar is optional.
> Look at this, it is "normal" not to have a bar after "function":
>
> Thanks that is the principal information that I needed.
>
> > More info: try to start reading the fine manual, because once you mastered reading
> type signatures you get authoritative information. First stop for more OCaml info
> is ocaml.org
>
> I have the "real worl ocaml" book and I know the main site too, the code I shown
> you came
> from : https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.ml
>
> In the same file I have this function too:
>
> let rec map f = function
>     [] -> []
>   | a::l -> let r = f a in r :: map f l
>
> And I don't get something :
>
> assuming we do something like that:
> a_fn is a function
> a_list is a two element list
>
> map a_fn a_list
>
> in the first call of the map function, we go through the line:
> a::l -> let r = f a in r :: map f l
>
> the first element is taken and we use it as an argument to the a_fn function. The
> result is then added to the result of the instruction
>
> map f l which trigger the line
>     [] -> []
>
> but it look like the a_fn is not applied to the last element.
>
> What am I missing ?
>
Maybe we just rewrite map (short names are idiomatic, but l as variable name
                                            is a bad choice IMO, prints like capital i):

let rec map f ls = match ls with
    [] -> []
  | elem :: rest -> let temp = f elem
                    in
                    temp :: map f rest

Do you still think f is not applied to the last element? The empty list is not the
last element,
but the end indicator.

/Str.