let N be with_zero set ; for S being non empty with_non-empty_values IC-Ins-separated Mem-Struct over N
for p being PartState of S
for i, j being Nat holds DecIC ((DecIC (p,i)),j) = DecIC (p,(i + j))
let S be non empty with_non-empty_values IC-Ins-separated Mem-Struct over N; for p being PartState of S
for i, j being Nat holds DecIC ((DecIC (p,i)),j) = DecIC (p,(i + j))
let p be PartState of S; for i, j being Nat holds DecIC ((DecIC (p,i)),j) = DecIC (p,(i + j))
let i, j be Nat; DecIC ((DecIC (p,i)),j) = DecIC (p,(i + j))
thus DecIC ((DecIC (p,i)),j) =
(p +* (Start-At (((IC p) -' i),S))) +* (Start-At ((((IC p) -' i) -' j),S))
by Th65
.=
(p +* (Start-At (((IC p) -' i),S))) +* (Start-At (((IC p) -' (i + j)),S))
by NAT_2:30
.=
DecIC (p,(i + j))
by FUNCT_4:114
; verum