Question

I have type

Variable l: list (a * b * option c * option d).
Variable ls : list (list l).

I would like to take the type option d from the head of the list and check the whole list after that. My code look like this:

Definition test (l: list (a * b * option c * option d)):=
match l with
| nil => ... (* not important *)
| (_,_,_,od) :: l' => 
  match od with
  | None => ... (* not important *)
  | Some d => if forallb (fun li => forallb (fun ci => do_something ci d)) ls) l'
  end
end.

My question is that the testing if forallb (fun li => forallb (fun ci =>do_something ci d))ls)l' I added forallb (fun li =>...)because I would like it test in the whole list l'. But I did not use the argument liat all.

EDIT: My question focus on the if forallb (fun li => forallb (fun ci => do_something ci d))ls)l'. I added forallb (fun li => because I would like to test on the rest of the list l'. Without forallb (fun li I can archive this test if (forallb (fun ci => do_something ci d))ls but I don’t know how to test this condition again in the list l'.

Answer 1

Your context is inconsistent.

Variable l : …

make that l is a list

Variable ls : list (list l).

assume that l is a type.

Maybe you meant:

Definition l := list (a * b * option c * option d).

Variable ls := list (list l).

This makes ls to be a list of list of lists (like a three-dimensional array).

Now, assuming that you meant do_something to have type l -> d -> bool

I guess you wanted to test do_something with all elements of type l in ls and all elements of type d in the argument of test (also called l, yuck).

you should have

…

|Some d => if forallb (fun li => forallb (fun ci => do_something ci d)) ls then test l’ else false
…

But frankly, your question leaves to much for the answerer to guess!