[m-users.] A neater way to call chained init functions?

[Julian Fondren]

On 2019-07-25 13:48, Julian Fondren wrote:
>   setup_sdl(Res1, !IO),
>   setup_sdlmix(Res2, !IO),
>   setup_sdlimg(Res3, !IO),
>   ( if all [X] (list.member(X, [Res1, Res2, Res3) => X = yes) then
>       io.write_string("sdl initialized\n", !IO)
>   else
>       io.write_string("somethign failed\n", !IO)
>   ).
> 
> That's the nondet list.member/2 btw.

Not a good use of it though, vs.:

   not list.member(no, [A, B, C])

or

   not (A = no; B = no; C = no)

or

   A = yes, B = yes, C = yes


A solution more like the monad one you want is to thread
initialization state through the initializers. This could involve a
lot of states, and terminate in a state telling you exactly what
failed, or on the simpler end it could just be a yes/no bool
stating whether initialization should continue, or an int that
gets incremented by each successful initialization:

   some [!N] (
     setup_sdl(0, !:N, !IO),
     setup_sdlmix(!N, !IO),
     setup_sdlimg(!N, !IO),
     ( if !.N = 3 then ...