Illegal dummy assignment example

The easiest way to get some statements to work with is going to be to import one of our existing interfaces; here we pick Interface:Classical_propositional_calculus.  import (PROPOSITIONAL Interface:Classical_propositional_calculus ) 

The only statement we care about from that file is: stmt (AntecedentIntroduction  (p → (q → p)))

Here's a valid proof:

 var (formula r s) thm (valid  (r → (s → r)) ( r s AntecedentIntroduction )) 

Here's one which produces a statement which has the right form, but the wrong variables.

 thm (invalid  (r → (s → s)) ( r s AntecedentIntroduction )) 