The
inc function increments
numeric_item, which is either a dictionary item or a numeric variable. If the optional numeric expression
increment_value is present, then the value of that expression is added to
numeric_item. If no expression is present, 1 is added to
numeric_item. The increment value can be negative or nonnegative.
inc(X) is essentially shorthand for
X = X + 1;
The function returns the sum of the numeric item and the increment value.