import MyNat.Definition
Tactic constructor
If the main goal's target type is an inductive type, constructor
solves it with
the first matching constructor, or else fails.
For example, if the goal is ⊢ P ∧ Q
then it finds the matching constructor And.intro
which has 2 parameters, so it solves the goal with two sub-goals, namely ⊢ P
and ⊢ Q
.