```    G4 Prover
Result of the test for sequent p->q->r <--> q->p->r

G4 Prover: a Prolog Prover for Roy Dyckhoff's Sequent Calculus G4
This prover is a fork made by Joseph Vidal-Rosset (joseph.vidal-rosset@gmail.com),
from seqprover.pl, the sequent prover for CL-X, written by Naoyuki Tamura (tamura@kobe-u.ac.jp).
Type "help." if you need some help.
fol(g4i)> fol(g4i).
yes
fol(g4i)> output(pretty).
yes
fol(g4i)> p->q->r<-->q->p->r.
Trying to prove with threshold = 0
Succeed in proving p->q->r --> q->p->r (1 msec.)
pretty:1 =
----------- Ax
q,r,p --> r
-------------- L0->1
q->r,q,p --> r
----------------- L0->1
p,q,p->q->r --> r
------------------ R->
q,p->q->r --> p->r
------------------- R->
p->q->r --> q->p->r
Trying to prove with threshold = 0
Succeed in proving q->p->r --> p->q->r (1 msec.)
pretty:2 =
----------- Ax
p,r,q --> r
-------------- L0->1
p->r,p,q --> r
----------------- L0->1
q,p,q->p->r --> r
------------------ R->
p,q->p->r --> q->r
------------------- R->
q->p->r --> p->q->r
yes
fol(g4i)> quit.
yes
Exit from Sequent Calculus Prover...
Total CPU time = 6 msec.
true

Back to g4-prover
Maintained by  Joseph Vidal-Rosset
```