auto type用途

標籤：

It is not uncommon to want to store the value of an expression in a variable. To
declare the variable, we have to know the type of that expression. When we write a
program, it can be surprisingly difficult—and sometimes even impossible—to
determine the type of an expression. Under the new standard, we can let the compiler
figure out the type for us by using the auto type specifier. Unlike type specifiers, such
as double, that name a specific type, auto tells the compiler to deduce the type
from the initializer.

auto item=val1+val2;

 以下語句是錯誤的：

auto a=0,b=3.14;//變數a與b類型不一致

auto要求在同一行內定義的變數類型一致

auto通常忽略頂層const，而不忽略底層const，如：

const int ci=i,&cr=ci;auto b=ci;//頂層const被忽略auto c=cr;//cr是頂層constci的別名auto e=&ci;//e是const對象的指標，e是底層const

若希望auto類型具有頂層const屬性，則需要顯示地聲明：

const auto b=ci;//此時b具有頂層const屬性

 

auto type用途