scope.cpp

#include <iostream>
using namespace std;
int main()
{
    // Up here, x is not in scope.
    // x = 0; // Error
    // Declare variable
    int x;
    // Scope of a variable is the locations in the program
    // where you can access it.
    // For 'x', up to the closing brace of main.
    x++;  // OK
    x = 9;

    if(x == 5)  // x is in scope
    {
        int y = x+1;
        // y is in scope for the rest of this
        // block in which it is declared.
    }
    // Once I leave the declaring block of y,
    // y is NOT in scope.
    //y++;  // ERROR

    // What about loops?

    int i;  // declare loop variable
    for(i = 0; i < 5; i++) // use loop variable
    {
    }
    // Can also access loop variable here

    for(int j = 0; j < 5; j++) // declare and use loop var
    {
        cout << j << "\n"; // can use loop var
    }
    // After loop, variable j is out of scope.

    // Cannot do a similar trick with while loops.
    int k = 0;
    while(k < 5)
    {
        k++;
    }

    // Can have two distinct vars with same name,
    // as long as the scopes are different.
    int myquiz = 99;  // scope is main
    if(myquiz > 80) {
        float myquiz = 2.35;
        cout << myquiz << "\n"; // refers to innermost in scope
    }
    cout << myquiz << "\n"; // refers to previous scope, the int






    return 0;
}