Just as unpleasant as it not emitting an error (as does DF6.0, by the way) is the result, $ ./a 3.000000 3.000000 3.000000 3.000000 3.000000 2. 000000 2.000000 2.000000 2.000000 ie. the addition continues one element beyond the length of a and still finds something from a to add to b..... Ugghhh!