C++ Using rand with if statement - c++

Question

I started C++ literally one day ago and I've been having a problem trying to create a rock, paper, scissors game. This code is not exactly how it will look when it's done, but I made this to demonstrate my issue.
I've made brps, meaning: bot rock paper scissors, a random number from 1-3 where the corresponding number will result in a cout stating what item the bot chose.
The rand part of the code was made from viewing different forums and answers to previous questions, but I can't seem to get this to work out. Whenever I run the program it says "Bot chose the rock" no matter what I do. However if I remove the if statemets, and simply print brps it shows a random number each time. So I need help to figure out why the program chooses the rock every single time when that choice should be defined by what number rand chooses.
Feel free to comment on other parts of the code as well, since I'm expecting it all to be somewhat poorly written :L
EDIT: urps is where the user inputs an answer. I didn't use it in this example.
#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;
int main()
{
cout<<"Hi! Welcome to ROCK PAPER SCISSORS!\n";
cout<<"To play, press enter.\n";
cin.get();
system("cls");
int game();
{
srand(time(NULL));
int brps = rand()>>4, urps;
brps = brps % 3 + 1;
cout<<"Bot chose ";
if (brps = 1){
cout<<"the rock.\n";}
else if (brps = 2){
cout<<"the paper.\n"; }
else if (brps = 3){
cout<<"the scissors.\n"; }
else{
cout<<"invalid.\n.";}
cin.get();
}
}

Answer 1

You should use == to compare, not =.
If you write brps = 1, you assign the value 1 to the variable brps, and the value of the assignment expression is then the same as the value that was assigned, that is, 1. This is non-zero, and gets converted to true, so you always get "the rock".
Also note that if your intension was to create a function called game, that is not what your code does. The extra semicolon makes it a declaration, saying that there is a function called game somewhere else, and then the { } block is just that, a { } block, not a function body.
And, as chris says in his comment, do turn on the compiler warnings. Different compilers give different warnings, but g++ gives the warning suggest parentheses around assignment used as truth value for your uses of = instead of ==. Compiler warnings is the compiler trying to help you, and programming is difficult enough that you shouldn't turn down any help.

Answer 2

You use the assignment operator = in your if statements which will assign the value 1 to brps and return a true value.
Use the operator == instead.
By the way: You do'nt call your game();.
Edit:
#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;
int game(); // This one declares the subroutine game()
int main()
{
int exit; /* 0 to continue, something else to exit the game */
cout<<"Hi! Welcome to ROCK PAPER SCISSORS!\n";
cout<<"To play, press enter.\n";
cin.get();
system("cls");
do { // This block will execute at least once
exit = game(); // This one calls the subroutine game()
} while (exit == 0); // ...and will execute again and again until exit != 0
return 0; // Or something useful
}
int game() // This implements the subroutine game()
{
srand(time(NULL));
int brps = rand()>>4, urps;
brps = brps % 3 + 1;
cout<<"Bot chose ";
if (brps == 1) {
cout<<"the rock.\n";
} else if (brps == 2) {
cout<<"the paper.\n";
} else if (brps == 3) {
cout<<"the scissors.\n";
} else{
cout<<"invalid.\n.";
}
cin.get();
if (some_kind_of_exit_condition) {
return 1; // results in exit == 1
}
return 0; // results in exit == 0
}
What I changed in your code:
The line int game(); in your code is neither a function call (since the syntax would be invalid) nor a implementation (because of the ;). The curly braces behind that line simply open a block in your code. This block is not necessary (but not forbidden, though). I changed the code to what I think you wanted to write:
I added a line int game(); at the very beginning that defines the subroutine game() that will enable the compiler to verify the call (in 2.)
I added a line game(); which actually calls the subroutine that is defined in 1.
I removed the ; after your int game(); to make a subroutine implementation of the block below.
I removed the } at the end and moved it to the end of main().
I added return statements at the end of both the main and the game routine.
I changed = to ==
Added a loop
Also note that the system("cls") will only work on systems where such a call exists. This is not very good code, since it it is platform dependent and will spawn at least one new process (perhaps more). In the abstract model of output streams there is no clear screen, since the output may also be a file or a printer (if you call your program with output redirection for example).
If you want to clear your screen, this can not be done with the standard output mechanism (except outputting a bunch of newlines - which is not very good since you don't know how many lines have to be written to clear the screen). If you want to do it better, you may use the Win32 Console API or libncurses. These libraries will enable you to control a visual terminal instead of the abstract line output the standard library gives to you. While the standard output is simple, these libraries aren't, so i'd recommend to continue using the cls but remember to change that later when you are more familar with c++.

Answer 3

You should only call srand() once, at the start of your program. Don't call it every time you need a random number, since this effectively re-initialized the generator.
There are other problems with the code:
1) The if (brps = 1) et al are assignments, not comparisons.
2) The
int game();
{
looks like it's defining a nested function, but it's not. Here game() is a prototype, and the stuff inside the curly braces is simply a nested block directly inside main(). I suspect this is not what you're trying to do.

Answer 4

This page covers the basics of randomization using rand(), srand(), etc. It may be worth a gander for you:
Furthermore, you should use the comparison operator (==), not the assignment operator (=) in your if comparisons; using = will actually set and change the value, and the comparison will be true every time since the result will be assigned to a non-zero value. Since your first if-comparison check succeeds every time for this reason, none of the other tests will even execute, and you'll get rock each time.

Answer 5

Please also note, to get as close to truly random number as possible you have to seed your random number generator with a changing number this is accomplished with: srand(time(0));
This can be placed anywhere before the actual call of the random number.
You will also have to #include <ctime> In order to be able to call time(0).