The auto Keyword

The auto Keyword

‘auto’ is undoubtedly the least used C++ keyword. This is because it’s always redundant. auto indicates local automatic storage type, for example:

 int main(){ auto int x; auto char  s[10];}size=3>

The more common form of declaring x and s is:

 int main(){ int x; // identical to auto int x; char  s[10]; // identical to auto char  s[10];}size=3>

Thus, ‘auto’ simply documents more explicitly the storage type of an object but it’s never really needed. In pre-standard C++, the default type of incomplete declarations such as the following was int:

 volatile x; // construed as 'volatile int x;'const y  = 0; // construed as 'const int y=0;'size=3>

In those days, you could also write:

 auto n; // equivalent to 'auto int n'size=3>

However, standard C++ doesn’t permit declarations with implicit int anymore. Consequently, ‘auto’ has become completely optional.


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