Algorithm 97: Shortest path

procedure arithmetic (a, b, c, op); integer a, b, c, op; ¢onlment This procedure will perform different order arithmetic operations with b and c, putting the result in a.The order of the operation is given by op.For op = 1 addition is performed.For op = 2 multiplicaLion, repeated addition, is done.Beyond these the operations are non-commutative.For op = 3 exponentiation, repeated multiplication, is done, raising b to the power c.Beyond these the question of grouping is important.The innermost implied parentheses are at the right.The hyper-exponent is always c.For op = 4 tetration, repeated exponentiation, is done.For op = 5, 6, 7, etc., the procedure performs pentation, hexation, heptation, etc., respectively.The routine was originally programmed in FORTRAN for the Control Data 160 desk-size computer.The original program was limited to tetration because subroutine recursiveness in Control Data 160 FORTRAN has been held down to four levels in the interests of economy.The input parameter, b, c, and op, must be positive integers, not zero; begin own integer d, e, f, drop; ifop = 1 then begina := h-4-c; go tol end ifop = 2 thend := 0; else d := 1; e := c; drop := op -1;