A ref performs the role of a mutable variable within a tactic.
Create a new reference r with initial value a, execute t r, and then delete r.
Read the value stored in the given reference.
Update the value stored in the given reference.
core.init.meta.ref
A ref performs the role of a mutable variable within a tactic.
Create a new reference r with initial value a, execute t r, and then delete r.
Read the value stored in the given reference.
Update the value stored in the given reference.