[m-users.] Higher-order predicates and functions and equivalence types.

[Volker Wysk]

Am Freitag, dem 27.08.2021 um 20:26 +0100 schrieb Sean Charles
(emacstheviking):
> Hi,
> 
> I have a type definition like this:
> 
> :- type tcon
>     --->    tcon(
>                 options  :: felt_options,
>                 output   :: list(rop),
>                 warnings :: lserror,
>                 errors   :: lserror,
>                 render   :: pred(instruction::in, string::in, string::out) is semidet
>                 % ENV[] stack can go in here too
>             ).
> 
> The `render` field, I wanted to be able to code this something like:
> 
>     render :: foo
> 
> where foo would have been defined as
> 
> :- type foo = (pred(instruction::in, string::in, string::out) is semidet).

I'm not sure, but you have the type and modes in your type "foo". I think
you can only have the type in a type synonym. You also need to equal signs.

Cheers,
Volker
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