Each space has its own name, the same name in different scopes may point to different entities.
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Scope: {} is usually separated.
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Effective area began with the statement name name to the end where the declaration is completed.
#include<iostream>
using namespace std;
int main() { int i = 10; for (int j = 0;j <= 10;j++) { } } - main braces defined before, with global scope (global scope).
- i is defined within the scope of the main functions, from the beginning until the end of the main function i can access it, but the main function can not be visited.
- j in the for loop, a for loop will not be able to access j.
Nested scope
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Scope is included called
内层作用域(inner scope). -
Contains other scopes scope called
外部作用域(outer scope). -
Allowing the inner scope to redefine the existing outer scope name.
#include<iostream>
using namespace std;
int a = 10; int main() { cout << a << endl; // （1）输出10 int a = 0; cout << a << endl; // （2）输出0 cout << ::a << endl; // （3）输出10 system("pause"); return 0; } - (1) output 10, as a defined in the global domain.
- (2) the output occurs after a re-definition of local variables, then the output current of a redefined scope.
- (3) the output of global scope defined by a (scope is left empty, the request occurs global scope).
Transfer from stray marmot blog, the original link: https: //www.jianshu.com/p/b768a90568b4