[Caml-list] How can I simulate dynamic types in OCaml?

[Caml-list] How can I simulate dynamic types in OCaml?

[sergey dyshel]

Hi

I like static type-checking in OCaml but sometimes I
need to implement some dynamic stuff (like a list of
values of different types). Is there a way to
do it in OCaml or at least simulate this?

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Re: [Caml-list] How can I simulate dynamic types in OCaml?

[Michael Tucker]

Hi,

  If you have a set of things of different types, but you know the types
ahead of time, then this is possible. You can consider the type of each
item in your set to be a complex type that consists of a flag and the
actual data. You could then make a list of things that have this complex
type. In OCaml, you could define a new type:

type combotype = INT of int | CHAR of char

Plus whatever other types you will allow in your list.

Then, an expression like:

[INT 1, CHAR 'a', INT 2, INT 2, CHAR 'b']

will be well-typed.

Does that help?

Mike

On Fri, 4 Apr 2003, sergey dyshel wrote:

> Hi
>
> I like static type-checking in OCaml but sometimes I
> need to implement some dynamic stuff (like a list of
> values of different types). Is there a way to
> do it in OCaml or at least simulate this?
>
> __________________________________________________
> Do you Yahoo!?
> Yahoo! Tax Center - File online, calculators, forms, and more
> http://tax.yahoo.com
>
> -------------------
> To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
> Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
>

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Re: [Caml-list] How can I simulate dynamic types in OCaml?

[Sven Luther]

On Fri, Apr 04, 2003 at 03:58:42AM -0800, sergey dyshel wrote:
> Hi
> 
> I like static type-checking in OCaml but sometimes I
> need to implement some dynamic stuff (like a list of
> values of different types). Is there a way to
> do it in OCaml or at least simulate this?

Use a list of variants ?

type element = A of a | B of b | C of c | D of d | ...

type liste = element list 

You have to check the appropriate variant each time (or most time) you
use it, but after all, you wanted dynamic type checking.

Friendly,

Sven Luther

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