The relationship between auto and decltype

Question

Is

auto x = initializer;

equivalent to

decltype(initializer) x = initializer;

or

decltype         


        

Answer 1

1. If initializer is an array then decltype(x) or decltype((x)) don't work simply on it. However auto will be deduced to a pointer.
2. If initializer is a function then applying decltype(fp) will deduce to the function type however, auto will deduce to its return type.

So in general auto cannot be considered as a replacement of any decltype() version you asked.