set FOR = for-up (a,i,n,I);
set i1 = (a,i) >=0_goto ((card I) + 3);
set i2 = AddTo (a,i,n);
set PF = ((Load ((a,i) >=0_goto ((card I) + 3))) ';' I) ';' (AddTo (a,i,n));
card (((Load ((a,i) >=0_goto ((card I) + 3))) ';' I) ';' (AddTo (a,i,n))) =
(card (((a,i) >=0_goto ((card I) + 3)) ';' I)) + 1
by SCMP_GCD:4
.=
((card I) + 1) + 1
by SCMPDS_6:6
.=
(card I) + (1 + 1)
;
then
(card (((Load ((a,i) >=0_goto ((card I) + 3))) ';' I) ';' (AddTo (a,i,n)))) + (- ((card I) + 2)) = 0
;
hence
for-up (a,i,n,I) is shiftable
by SCMPDS_4:23; verum