Question

Please have a look at the following code

#include <iostream>
#include <stdlib.h>
#include <ctime>

using namespace std;

int main()
{
    enum Movement{STAND=1,WALK,RUN,CRAWL};

    srand(time(0));
    Movement state = (Movement)(1+rand()%4);

    for(int i=0;i<10;i++)
    {

    cout << state << endl;

    switch(state)
    {
        /*Here the logic is,
         * 
         * 1. From stand, he can walk or crawl
           2. From Walk, he can stand or run
           3. From Run, he can walk
           4. From Crawl, he can stand
         */

        case STAND: 
            cout << "You can walk or crawl" << endl;        
            while(state==WALK || state==CRAWL)
            {
                state = (Movement)(1+rand()%4);
            }
            break;


        case WALK: 
            cout << "You can stand or run" << endl;
            while(state==STAND || state==RUN)
            {
                state = (Movement)(1+rand()%4);
            }
            break;


        case RUN: 
            cout << "You can walk" << endl;
            while(state==WALK)
            {
                state = (Movement)(1+rand()%4);
            }
            break;

        default: 
            cout << "You can stand" << endl;
            while(state==STAND)
            {
                state = (Movement)(1+rand()%4);
            }

    }

    }
}

I am using random, and expecting random results based on those given conditions. But I am getting the same result as below.

2
You can stand or run
2
You can stand or run
2
You can stand or run
2
You can stand or run
2
You can stand or run
2
You can stand or run
2
You can stand or run
2
You can stand or run
2
You can stand or run
2
You can stand or run

why is this? I have tried do..while loops as well. No good at all. Nothing is checking the conditions I have given in case statements. please help.

Answer 1

Flip your while-loops to do-while. The expressions are invalid as well for the checks (unless it was your intention they NOT match the text). The states, according to the messages are:

Stand ==> (Walk || Crawl)
Walk  ==> (Stand || Run)
Run   ==> (Walk)
Crawl ==> (Stand)

So the sections need to be changed to

1. Generate the new random number BEFORE checking it. and..
2. Not leave until a valid production is reached.

The latter part is important for the Run and Crawl states. Since they can only produce ONE valid result state, spinning a rand() call looking for that value makes no sense. Just set the new state and loop again.

Regarding (2) above:

    case WALK: 
        cout << "You can stand or run" << endl;
        while(state==STAND || state==RUN)
        {
            state = (Movement)(1+rand()%4);
        }
        break;

Becomes…

    case WALK: 
        cout << "You can stand or run" << endl;
        do {
            state = (Movement)(1+rand()%4);
        } while(state!=STAND && state!=RUN);
        break;

Regarding the Run and Crawl states:

    case RUN: 
        cout << "You can walk" << endl;
        state = WALK;
        break;

    default: // CRAWL 
        cout << "You can stand" << endl;
        state = STAND;
        break;

That leaves you one more to check yourself, which I leave to you.