How can I write the same code using switch statement and the full word instead of initials?

Question

Please consider the following code:

#include <iostream>

using std::cin;
using std::cout;
using std::endl;
int main(int argc, char** argv) {
    enum object {rock, paper, scissors};
    object player1, player2;
    cout << " "Enter "r" for rock, "p" for paper or "s" for scissors:";
    char p1, p2;
    cin >> p1 >> p2;

    if (p1 == 'r') {player1 = rock;}
    else if (p1 == 'p') {player1 = paper;}
    else if (p1 == 's') {player1 = scissors;}
    else {cout << "invalid input, play again" << endl; exit(1);}

    if (p2 == 'r') {player2 = rock;}
    else if (p2 == 'p') {player2 = paper;}
    else if (p2 == 's') {player2 = scissors;}
    else {cout << "invalid input, play again" << endl; exit(1);}

    if (player1==player2) cout <<"objects are equal";
    else if (player1==rock && player2==paper) cout << "player 2 is the winner";
    else if (player1==rock && player2==scissors) cout<<"player 1 is the winner";
    else if (player1==paper && player2==rock) cout << "player 1 is the winner";
    else if (player1==paper && player2==scissors) cout <<"Palyer 2 is the winnder";
    else if (player1==scissors && player2==paper) cout << "Player 1 is winner";
    else cout <<"Player 2 is the winner";
    cout << endl;
}

How can the above code be rewritten with the switch statement while the user has to give the full word (rock, paper, scissors) instead of the initials for the input.

Update: I have converted part of the code with switch, but I was interested to see if I could use it for the entire code:

For instance:

switch (p1) {
        case 'r': player1=rock; break;
        case 'p': player1=paper; break;
        case 's': player1=scissors; break;
    }

instead of

if (p1 == 'r') {player1 = rock;}
    else if (p1 == 'p') {player1 = paper;}
    else if (p1 == 's') {player1 = scissors;}
    else {cout << "invalid input, play again" << endl; exit(1);}

Granted there are only 3 items, but you could use a `std::map` to get rid of the `switch` and a lot of those `if / else` statements. — PaulMcKenzie, Nov 12 '19 at 16:34
@VladfromMoscow Why reopen? The OP wants to switch on strings, the dupe says they can't — NathanOliver, Nov 12 '19 at 16:38
@VladfromMoscow If you wan to add something, you add it to the dupe, you don't reopen the question. Now the information is segregated instead of integrated, — NathanOliver, Nov 12 '19 at 16:41

Lukas-T · Answer 1 · 2019-11-12T17:47:56.087

1

You can't do it this simple. switch does not work with strings. You could however circumvent this problem and calculate the object before doing the switch:

std::string player1Input, player2Input;
//...
std::cin >> player1Input >> player2Input;

object player1Choice = getChoice(player1Input);
object player2Choice = getChoice(player2Input);

Where getChoice could look like this:

object getChoice(std::string input)
{
    if(input == "rock")
        return object::rock;
    else if(input == "paper")
        return object::paper;
    else if(input == "scisor")
        return object::sciscor;
    else {
        //invalid input
    }
}

Then you can use your switch:

switch(player1Choice)
{
case object::rock:
    switch(player2Choice)
    {
    case object::rock: //rock vs rock
        break;
    ...
    };

    break;
...
}

edited Nov 12 '19 at 17:47

answered Nov 12 '19 at 16:39

Lukas-T

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I think this is a good solution to my question. But I get the error "Use of undeclared identifier 'player1'" for cin << player1 << player2; How can I get rid of that? – developer Nov 12 '19 at 17:43
@developer oops, sorry, that's a typo, I fixed it :) – Lukas-T Nov 12 '19 at 17:44
Now I getting this error: Invalid operands to binary expression ('std::__1::istream' (aka 'basic_istream') and 'std::__1::string' (aka 'basic_string, allocator >')) – developer Nov 12 '19 at 17:47
Yes, I think I need a break. – developer Nov 12 '19 at 18:00
@developer I meant myself, because of the two typos ;) but breaks are always good ^^ – Lukas-T Nov 12 '19 at 18:09
Yes, I agree with that :) – developer Nov 12 '19 at 18:16
I get (Function definition is not allowed here) for (object getChoice (string input){) – developer Nov 12 '19 at 19:21
That's three different pieces of code. I trust you to put them where they are needed ;) – Lukas-T Nov 12 '19 at 20:04

score 0 · Answer 2 · answered Nov 12 '19 at 16:25

0

It can't.

switch works on built-in types, like int, bool and char.

It is not a complex comparison feature that can perform checks on strings.

answered Nov 12 '19 at 16:25

Lightness Races in Orbit

378,754
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1,055

Thank you! So that is why the original code uses initials instead of the full words. – developer Nov 12 '19 at 16:47
@developer Yep, probably. – Lightness Races in Orbit Nov 12 '19 at 17:07

Vlad from Moscow · Answer 3 · 2019-11-12T16:52:15.920

It seems you mean something like the following

#include <string>
#include <iterator>
#include <algorithm>

//...

const char * object_name[] = { "rock", "paper", "scissors" };
enum object {rock, paper, scissors};

std::string choice;
std::cin >> choice;

//...

auto it = std::find_if( std::begin( object_name ), std::end( object_name ),
                        [&choice]( const char *item )
                        {
                            return choice == item;
                        } );

if ( it != std::end( object_name ) )
{
    int p1 = std::distance( std::begin( object_name ), it );

    switch ( p1 )
    {
    case rock:
        //...
        break;
    case paper:
        //...
        break;
    case scissors:
        //...
        break;
    }
}

Here is a demonstrative program

#include <iostream>
#include <string>
#include <iterator>
#include <algorithm>

int main() 
{
    const char * object_name[] = { "rock", "paper", "scissors" };
    enum object {rock, paper, scissors};

    std::string choice;

    std::cout << "Enter \"" << object_name[0] << "\", or \""  << object_name[1]
              << "\", or \"" << object_name[2] << "\": ";
    std::cin >> choice;

    auto it = std::find_if( std::begin( object_name ), std::end( object_name ),
                        [&choice]( const char *item )
                        {
                            return choice == item;
                        } );

    if ( it != std::end( object_name ) )
    {
        int p1 = std::distance( std::begin( object_name ), it );

        switch ( p1 )
        {
        case rock:
            std::cout << object_name[rock];
            break;

        case paper:
            std::cout << object_name[paper];
            break;
        case scissors:
            std::cout << object_name[scissors];
            break;
        }
    }

    return 0;
}

Its output might look like

Enter "rock", or "paper", or "scissors": paper
paper

Thanks but I think this one is beyond the limits of my current knowledge of cpp coding. I am trying to explain the lines to myself. — developer, Nov 12 '19 at 16:50
@developer See the demonstrative program added to my answer. — Vlad from Moscow, Nov 12 '19 at 16:52

How can I write the same code using switch statement and the full word instead of initials?

3 Answers3