[Caml-list] Case insensitive in type

[Caml-list] Case insensitive in type

[Nicolas Ratier]

Hello,

We use the type :

type term =
   | Term of string * term list
   | Var  of string * int
;;

I would like the string of the Term constructor not to be case sensitive,
for example, all the following terms should be the same :
Term("Plus",[...])
Term("plus",[...])
Term("PLUs",[...])

Is it possible ?
Thanks,

Nicolas

Re: [Caml-list] Case insensitive in type

[Daniel Bünzli]

Le mercredi, 2 juillet 2014 à 09:34, Nicolas Ratier a écrit :
> I would like the string of the Term constructor not to be case sensitive,
> for example, all the following terms should be the same :

[...]  
> Is it possible ?

The only way to do this is to make the type private and always construct term values through a constructor which normalizes the strings.  

type term = private Term of string * term list
let term s args = Term ((String.lowercase s), args)  

Best,

Daniel

Re: [Caml-list] Case insensitive in type

[Gabriel Kerneis]

On Wed, Jul 02, 2014 at 09:43:13AM +0100, Daniel Bünzli wrote:
> Le mercredi, 2 juillet 2014 à 09:34, Nicolas Ratier a écrit :
> > I would like the string of the Term constructor not to be case sensitive,
> > for example, all the following terms should be the same :
> 
> [...]  
> > Is it possible ?
> 
> The only way to do this is to make the type private and always
> construct term values through a constructor which normalizes the
> strings.  
> 
> type term = private Term of string * term list
> let term s args = Term ((String.lowercase s), args)  

It will not help with pattern-matching, though. The following will fail:

match (term "plus" []) with
| Term("Plus",[]) -> true
| _ -> assert false

I don't think there is a way to work around this.
-- 
Gabriel

Re: [Caml-list] Case insensitive in type

[Daniel Bünzli]

Le mercredi, 2 juillet 2014 à 10:30, Gabriel Kerneis a écrit :
> It will not help with pattern-matching, though. The following will fail:
>  
> match (term "plus" []) with
> | Term("Plus",[]) -> true
> | _ -> assert false
>  
> I don't think there is a way to work around this.
Yeah sure, the pattern matches you write have to follow the normalization. A work around is to make the string abstract and then check via a when clause.

match (term "plus" []) with  
| Term (f, []) when f = Term.name "Plus" -> true
| _ -> assert false

Daniel