Prover for G4ip (LJT)  
Readme
Formulae:    
    F ::= false 
    | A 
    | F & F 
    | F v F 
    | F -> F 
    | F <-> F
    | (F)
Sequents:     => F     or 
                     [F,]* F => F
Inference Rules: 
html,
dvi or 
ps.
Start: starts the proof search, 
Clear: clears the text fields,
Next:  searches for the next proof,
Stop:  stops the proof search.
Provable Examples:
-              => (p v (q v r)) <-> ((p v q) v r)
-              => (p & (q & r)) <-> ((p & q) & r)
-              => (p & (q v r)) <-> ((p & q) v (p & r))
-              => (p v (q & r)) <-> ((p v q) & (p v r))
-              => (p -> p) -> (p -> p)
-              => (a -> (b -> c)) -> ((a -> b) -> (a -> c))
-              => a -> ((a -> b) -> a)
-              => b -> ((a -> b) -> b)
-              => (a & b) -> (b & a)
-              => (a -> (a -> b)) -> (a -> b)
-              => ((((p -> q) -> p) -> p) -> q) -> q
-              => (a v (a -> b)) -> (((a -> b) -> a)-> a)
-              => (a -> (b -> false)) -> (b -> (a -> false))
-              => ((a v (a -> false))-> false)-> false
- a & b, c & d => b & c
- (a v (a-> false)) -> false => false
Non-Provable Examples:
-              => ((a -> b) -> a) -> a
-              => a v (a -> false)
-              => (a & b v (((( a-> flase) -> false) -> q) v (b -> q)) -> q) -> q
Some advanced examples
Source Code:
Formulae,
Contexts,
Sequents,
ProofDisplay,
Prover,
Parser,
Applet
Lambda Prolog Version: The programm 
G4ip.mod can be executed using  
Terzo
Another implementation of G4ip by Joshua Hodas and Dale Miller written in 
Lolli can be found
here.
Christian Urban
Last modified: Sun May 10 18:18:28 GMT 1998