DiM(X, Y)
DiM: INTEGER or REAL function, the exact type being the result of cross-promoting the
types of all the arguments.
X: INTEGER or REAL; scalar; INTENT(IN).
Y: INTEGER or REAL; scalar; INTENT(IN).
Intrinsic groups: (standard FORTRAN 77).
Description:
Returns X-Y if X is greater than Y; otherwise returns zero.