:: deftheorem defines sum SCPINVAR:def 1 :
for n, p0 being Element of NAT holds sum (n,p0) = ((((GBP := 0) ';' ((intpos 1) := 0)) ';' ((intpos 2) := (- n))) ';' ((intpos 3) := (p0 + 1))) ';' (while<0 (GBP,2,(((AddTo (GBP,1,(intpos 3),0)) ';' (AddTo (GBP,2,1))) ';' (AddTo (GBP,3,1)))));