What am I doing wrong in my program?

Question

1.00/5 (1 vote)

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C++

int main(int argc, char** argv) 
{
    string stopLightColor = "" ;
    cout << "Please enter what your stoplight color is: " << endl ;
    cin >> stopLightColor;
    if (stopLightColor == "red" || "yellow") {
        cout << "Please stop." << endl ;
    }
    else if (stopLightColor == "green") 
    {
        cout << "Continue" << endl ;
    }

    return 0 ;
}

No matter what I type in, the answer always is "Please stop."

What I have tried:

I haven't necessarily tried anything new because I don't know what I could fix about it.

Posted 21-Apr-16 16:20pm

Member 12477055

Updated 21-Apr-16 20:45pm

Garth J Lancaster

v2

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3 solutions

Solution 1

Quote:
What am I doing wrong in my program?

Because you don't know the C++ syntax.
Learn really C++ by reading documentation and follow tutos.
Pay particular attention to logical operators.

Posted 21-Apr-16 16:37pm

Patrice T

Updated 21-Apr-16 16:50pm

v2

Comments

Member 12477055 21-Apr-16 22:40pm

That's what I need help with. What is the error? :p

Sergey Alexandrovich Kryukov 22-Apr-16 0:12am

I disagree. This is not about knowing the syntax, this is worse: not trying to think logically.
Moreover, formally, the syntax is correct. Correct solution is Solution 2. (I did not vote this time.)
—SA

Solution 3

As others already suggested you misunderstood how conditional expressions works in C++. That said, I suppose there ways to improve your code. I suppose there are two scenarios:

(1) You trust the semaphore (the user input) to be either 'red' or 'yellow' or 'green'.
In such scenario, the code could be written simply

C++

if (stopLightColor == "green")
{
  cout << "Continue" << endl;
}
else // it IS either 'red' or 'yellow', don't bother to check
{
  cout << "Please stop" << endl;
}

(2) You allow the semaphore (the user input) to be broken, at times.
In such a scenario you HAVE to handle the 'broken' eventuality.

C++

if (stopLightColor == "green")
{
  cout << "Continue" << endl;
}
else if ( stopLightColor == "yellow" || stopLightColor == "red")
{
  cout << "Please stop" << endl;
}
else // the semaphore is broken
{
  cout << "Warning: the semaphore is broken, please go on very carefully" << endl;
}

Posted 21-Apr-16 20:45pm

CPallini

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Garth J Lancaster · Accepted Answer · 2016-04-21T16:41:00

Solution 2

As ppolymorphe has suggested, look at this line

if (stopLightColor == "red" || "yellow")

can you think of the correct way it should be written ?

Posted 21-Apr-16 16:41pm

Garth J Lancaster

Comments

Member 12477055 21-Apr-16 22:43pm

Only thing I can think of is getting rid of the "". I feel like the or operator is in the correct spot.

Garth J Lancaster 22-Apr-16 0:00am

the "" are fine, and the or operator IS in the correct spot

the issue is,

a == b || c

the || c always gives you a false

so you need to write

a == b || a == c

get it ? (thats as close as I can without actually typing it for you)

Sergey Alexandrovich Kryukov 22-Apr-16 0:11am

Correct, a 5.
—SA