Ltac position argument for instantiate

Question

The tactic instantiate can take and ident or a num as:

instantiate (ident:= term)

instantiate (num := term)

Now I want to use the second one inside a tactic definition. For example:

  Ltac my_instantiate n x:=
    instantiate(n:=x).

Unfortunately, this gives the following error:

Ltac variable n is bound to 1 which cannot be coerced to a fresh identifier.

I suspect that ltac is trying to use the first use of instantiate. How do I tell coq to instantiate by position, or how do I pass the argumetn correctly?

Here is a minimal example:

Ltac my_instantiate n x:=
  instantiate(n:=x).
Goal exists x, x = 2.
  eexists.
  my_instantiate 1 2.
  (* Fails with: Ltac variable n is bound to 1 which 
     cannot be coerced to a fresh identifier. *)

Note: I know that instantiating by position is discouraged, but I'm only using my tactic for exploration purposes.

score 0 · Answer 1 · answered Dec 05 '18 at 09:27

0

Maybe what you are looking for can be expressed in terms of a Tactic Notation?

reference manual - tactic notations

answered Dec 05 '18 at 09:27

hyperlinq

31
5

Best I can come up with is `Tactic Notation "my_instantiate" integer(n) ident(x):= instantiate(n:=x).` which still doesn't work. Would you mind sharing what you have in mind? – user2506946 Dec 05 '18 at 22:35
1

This seems like a bug in Coq, and worth reporting as such – Jason Gross Dec 09 '18 at 07:00
1

@user2506946 i had something like that in mind. Why it doesn't work is unclear to me. – hyperlinq Dec 12 '18 at 10:21

Ltac position argument for instantiate

1 Answers1