I _ _ _ _ _ _ _ _ _ _ _ _ constant

REDUCE knows i is the square root of -1, and that i^2 = -1.

examples:

(a + b*i)*(c + d*i); 

  A*C + A*D*I + B*C*I - B*D 


i**2; 

  -1

icannot be used as an identifier. It is all right to use i as an index variable in a for loop, or as a local (scalar) variable inside a begin...end block, but it loses its definition as the square root of -1 inside the block in that case.

Only the simplest properties of i are known by REDUCE unless the switch complex is turned on, which implements full complex arithmetic in factoring, simplification, and functional values. complex is ordinarily off.