lean4-htt/tests/lean/run/induction_tactic_delta.lean
Leonardo de Moura f650a1b873 refactor(library/init/meta): avoid '_core' idiom using default parameters
I kept a few core methods (e.g., exact_core and apply_core). Reason:
if we use default parameters

    meta constant exact (e : expr) (md := semireducible) : tactic unit

then, we will not be able to write

    to_expr p >>= exact

The workaround is

    do t <- to_expr p, exact t

or
    to_expr p >>= (fun x, exact x)

One alternative is to change how we handle default parameters, and
eta-expand applications that involve default parameters.
We may also have an attribute [eta_expand]. Then

    attribute [eta_expand] foo

instructs the elaborator to automatically eta-expand foo-applications.
The attribute would give users more control, and avoid potential
performance problems. Without the attribute, then for every function
application the elaborator has to check the type and decide whether it
must be eta-expanded or not.

@gebner @kha What do you think?
2017-02-14 09:46:55 -08:00

15 lines
364 B
Text

open tactic
-- This test makes sure that [foo'] is not unfolded in the major premise,
-- since [foo'] is the type of the major premise of the provided recursor.
inductive foo (n : nat)
| mk : foo
definition foo' := @foo 0
definition foo'.rec := @foo.rec
example : Pi (x : foo'), x = x :=
by do x ← intro `x,
induction x `foo'.rec [],
reflexivity