> auto x1=1., x2=2., x3=3., x4=4., x5=5, x6=6.; If the coder wanted them to all be doubles, it's easy to require that by just saying so, and then even x5 will be a double. double x1=1., x2=2, ... So it seems to me that auto does exactly what you asked it to here, and I actually prefer this behavior for conciseness and expressiveness sake.