DEFINITION and4_rec()
TYPE =
       ΠP0:Prop
         .ΠP1:Prop
           .ΠP2:Prop
             .ΠP3:Prop.ΠP:Set.(P0→P1→P2→P3→P)→(and4 P0 P1 P2 P3)→P
BODY =
λP0:Prop
         .λP1:Prop
           .λP2:Prop
             .λP3:Prop
               .λP:Set
                 .λf:P0→P1→P2→P3→P.λH:and4 P0 P1 P2 P3.<λH1:and4 P0 P1 P2 P3.P> CASE H OF and4_intro H1 H2 H3 H4⇒f H1 H2 H3 H4