36 lines
1,013 B
Text
36 lines
1,013 B
Text
|
Variable list : Type -> Type
|
||
|
|
Variable nil {A : Type} : list A
|
||
|
|
Variable cons {A : Type} (head : A) (tail : list A) : list A
|
||
|
|
Definition n1 : list Int := cons (nat_to_int 10) nil
|
||
|
|
Definition n2 : list Nat := cons 10 nil
|
||
|
|
(*
|
||
|
|
The following example demonstrates that the expected type (list Int)
|
||
|
|
does not influece whether coercions are used or not.
|
||
|
|
*)
|
||
|
|
Definition n3 : list Int := cons 10 nil
|
||
|
|
|
||
|
|
(*
|
||
|
|
Here are some workarounds for the example above.
|
||
|
|
The 'let' construct is one of the main tools for providing
|
||
|
|
hints.
|
||
|
|
*)
|
||
|
|
Definition n3a : list Int :=
|
||
|
|
let a : Int := 10
|
||
|
|
in cons a nil
|
||
|
|
|
||
|
|
(* Solution b: we manually provide the coercion *)
|
||
|
|
Definition n3b : list Int := cons (nat_to_int 10) nil
|
||
|
|
|
||
|
|
(* The folowing example works *)
|
||
|
|
Definition n4 : list Int := nil
|
||
|
|
|
||
|
|
(*
|
||
|
|
The following example demonstrates that we do not do type inference.
|
||
|
|
In the current implementation, we first elaborate the type and
|
||
|
|
then the body.
|
||
|
|
*)
|
||
|
|
Definition n5 : _ := cons 10 nil
|
||
|
|
|
||
|
|
Set pp::coercion true
|
||
|
|
Set pp::implicit true
|
||
|
|
Show Environment 1.
|