A more intuitive mechanism for referencing to the last introduced free variable.
Context
Currently there is no way to reference the last included free variable, making so that the only way of closing a term is by leaving the current level first, which is painful at some points and generate some uglier code, this PR changes the mechanism, to make so that the current level is actually the same of the last included free varfiable.
Goals
A more intuitive mechanism for referencing to the last introduced free variable.
Context
Currently there is no way to reference the last included free variable, making so that the only way of closing a term is by leaving the current level first, which is painful at some points and generate some uglier code, this PR changes the mechanism, to make so that the current level is actually the same of the last included free varfiable.