C++ Variables, Conditionals, Loops, Functions, just a feel.

Are you local? Or global? private or public?

    // Struct members are default public
    struct x {
        int a;
        float b;
        char c[10];
    };
    // class members are default private
    class z {
        int a;
        float b;
        char c[10];
      public:
        int getvalue() const;
        void setvalue( int v );
    };

Conditionals

#include <iostream>
#include <cstdio>
#include <cstdint>

int main()
{
    const int ZERO = 0;
    const int ONE = 1;
    const int TWO = 2;
    const int THREE = 3;

    int x = 42;
    int y = 73;
    if ( x < y ) {
    } else if ( y > x ) {
    } else {
    }

    // ternary
    printf ("This number is greater : %d\n", x > y ? x : y );

    switch (x) {
        case ZERO: cout << ZERO << endl; break;
        case ONE: cout << ONE << endl; break;
        case TWO: cout << TWO << endl; break;
        case THREE: cout << THREE << endl; break;
        case 42: cout << 42 << endl; break;
        case 52: cout << 52 << endl; break;
        default: cout << 99 << endl; break;
    }
}

Loops

#include <iostream>
#include <cstdio>

int main() {
    int array[] = { 1,2,3,4,5 };
    char string[] = "string";

    auto j = 3;
    for( auto i : array ) {
        printf( "i is %d\n", i );
    }

    // c++ range based loop
    // range based loop is a compile time feature so compiler knows the size and type
    for ( int i : array ) {
        printf( "* %d / ", i );
    }
    printf( "\n" );
    // for ( char c : "abcdef" ) { // this works too!!
    // for ( char i : string ) { // this works too!!
    for ( int i : string ) { // int works with char too!!
        printf( "* %c / ", i );
    }
    printf( "\n" );

    // for ( int i = 0; string[i]; i++ ) { // last char in a string is '0', == false 
    for ( char *cp = string; *cp ; ++cp ) {
        printf( "* %c / ", *cp );
    }
    cout << endl;

    for (int i = 0; i < j; i++) {
    }

    int i = 0;
    while (i < 5) {
        if ( i == 2 ) {
            i++; // important!!
            continue;
        } else if ( i == 3 ) {
            break;
        }
        i++;
    }

    do {
        i--;
    } while ( i > 0 );
}

Functions

#include <cstdio>
#include <iostream>
#include <string>
using namespace std;
using std::cin;
using std::cout;

void func( const string * fs )
{
        printf( "value is %s\n", fs->c_str());
}

int main( int argc, char * argv[] )
{
        string s = "hello im a string";
        puts( "this is main()" );
        func(&s);
        printf( "string is %s\n", s.c_str());
        for (int i=0; argv[i]; i++ ) {
                printf( argv[i] );
                printf( "%d: %s\n", i, argv[i] );
        }
        return 0;
}

Using namespace or else

#include <cstdio>
#include <iostream>
#include <string>
using namespace std;

// Another way
#include <cstdio>
using std::puts;
using std::printf;
#include <iostream>
using std::cin;
using std::cout;