How the fuck do you use Boolean variable

[multitasker451]

I'm trying to write a program (C++) for an assignment and I'm really strugglin with Boolean variables.  Basically, the user is asked if there are fish present, and then they are supposed to input a 1 (yes/true) or a 0 (no/false).  The result then leads to a water volume calculation.  Here's what I have (with unrelated stuff removed):

 

float water_volume;

float tank_volume;

bool areFishPresent;

 

cin >> areFishPresent;

 

//make water volume calculations

if (areFishPresent == true){

  water_volume = tank_volume - (areFishPresent * 2);

}

else (areFishPresent == false);{

  water_volume = tank_volume;

}

 

please help.  When I try to run it I get a message that says "floating point exception (core dumped)."

[Windows 10]

Calm down, no need for foul langauge

[multitasker451]

Just now, Windows 10 said:

Calm down, no need for foul langauge

sorry I've been working on this for so long

[scottyseng]

4 minutes ago, multitasker451 said:

-snip-

You just need else for the last statement. No need for "(areFishPresent == false);"

 

I'm also guessing you have some other code before this where you actually set areFishPresent to true or false based on user input?

[multitasker451]

 

Just now, scottyseng said:

You just need else for the last statement. No need for "(areFishPresent == false)"

I got the same message after running it

[79wjd]

if(areFishPresent){

     do stuff

} else { 

     do stuff

}

 

Now, if you wanted to add a third option (obviously this wouldn't apply for booleans), then something like this: 

int x = ____; //get user input

if(x == 0){

         do this stuff;

} else if (x == 1) {

       do this other stuff;

} else {

       do this

}

[scottyseng]

Just now, multitasker451 said:

 

I got the same message after running it

I also saw that you had a semi colon after (areFishPresent == false)

[multitasker451]

1 minute ago, scottyseng said:

You just need else for the last statement. No need for "(areFishPresent == false)"

 

I'm also guessing you have some other code before this where you actually set areFishPresent to true or false based on user input?

I don't think I can set it to true or false for this scenario since the user of the program is supposed to input whether it is true or false

[multitasker451]

Just now, scottyseng said:

I also saw that you had a semi colon after (areFishPresent == false)

I deleted that after deleting (areFishPresent == false)

[multitasker451]

The whole code:

 

#include<iostream>

using namespace std;

int main()
{
  int length;
  int width;
  int height_ft;
  int height_in;
  float tank_volume;
  float water_volume;
  bool areFishPresent;
  float waste_mass;
  int fish1;

 

//display welcome message
  cout <<"Welcome to the Fish Tank Computer" << endl;
  cout <<"Enter the following information:" << endl;

 

//user inputs length
  cout <<"Please enter the length of the tank in feet" << endl;
  cin >> length;

 

//user inputs whether fish are present
  cout <<"Are fish present (1 - yes, 0 - no)?" << endl;
  cin >> areFishPresent;

 

//make width and height calculations
  width = length * (1.0/4.0);
  height_ft = length * (2.0/3.0);

 

//make water volume calculations
  if (areFishPresent == true){
    water_volume = tank_volume - 2;
  }
  else{
    water_volume = tank_volume;
  }

 

//determine number of fish the tank can hold
  fish1 = water_volume / 25;

 

//determine amount of nuclear waste required
  height_in = height_ft / 12;
  waste_mass = 11 / height_in;

 

//output measurements
  cout <<"Your tank dimensions are:" << endl;
  cout << "length" << length << "ft" << endl;
  cout << "width" <<  width << "ft" << endl;
  cout << "height" << height_ft << "ft" << endl;
  cout << "tank cap" << tank_volume << "gals" << endl;
  cout << "water" << water_volume << "gals" << endl;
  cout << "waste" << waste_mass << "rads" << endl;
  cout << "Your tank will hold:" << fish1 << "fish." << endl;
  cout << "Thank you for using the Fish Tank Computer." << endl;

  return 0;
}

 

[79wjd]

 

float water_volume;

float tank_volume;

bool areFishPresent;

 

cin >> areFishPresent;

 

//make water volume calculations

if (areFishPresent == true){

  water_volume = tank_volume - (areFishPresent * 2); // WHAT IS THIS LINE DOING?

}

else  {

  water_volume = tank_volume;

}

 

 

I'm not positive if you can cin a boolean. Try using an int instead. 

 

What is 2*true? 

[scottyseng]

1 minute ago, multitasker451 said:

I deleted that after deleting (areFishPresent == false)

Ah, the other thing I'm seeing is that you're trying to multiply areFishPresent by 2...

water_volume = tank_volume - (areFishPresent * 2); 

You can't multiply a Boolean variable.

[79wjd]

Make areFishPresent an int. 

[scottyseng]

2 minutes ago, multitasker451 said:

-snip-

You don't really need a Boolean variable at all, you can just have the if statement check if areFishPresent is equal to 1 (after turning it into a int).

[multitasker451]

OK, the person potentially using this program is supposed to enter a 1 (for yes/true) or a 0 (for no/false) when asked if fish are present.  Depending on their answer, the water volume is calculated.

[multitasker451]

5 minutes ago, scottyseng said:

Ah, the other thing I'm seeing is that you're trying to multiply areFishPresent by 2...

water_volume = tank_volume - (areFishPresent * 2); 

You can't multiply a Boolean variable.

OK, I see that now, that was wrong, but I'm still getting the message.  I'm going to update the code above

 

[79wjd]

1 minute ago, multitasker451 said:

OK, I see that now, that was wrong, but I'm still getting the message.  I'm going to update the code above

 

Are you still using a boolean or did you change it to an int? 

[scottyseng]

4 minutes ago, multitasker451 said:

OK, the person potentially using this program is supposed to enter a 1 (for yes/true) or a 0 (for no/false) when asked if fish are present.  Depending on their answer, the water volume is calculated.

Do this after turning areFishPresent to a int instead of a boolean:

if (areFishPresent == 1){
	water_volume = tank_volume - 2;
} else {
	water_volume = tank_volume;
} 

 

[multitasker451]

Just now, djdwosk97 said:

Are you still using a boolean or did you change it to an int? 

changing it to int doesn't do anything

[79wjd]

Just now, multitasker451 said:

changing it to int doesn't do anything

Paste a new copy of the code, and use code brackets.

 

[code.]

 

[/code.]

[multitasker451]

3 minutes ago, djdwosk97 said:

Paste a new copy of the code, and use code brackets.

 

[code.]

 

[/code.]

using namespace std;

int main()
{
  int length;
  int width;
  int height_ft;
  int height_in;
  float tank_volume;
  float water_volume;
  int areFishPresent;
  float waste_mass;
  int fish1;

 

//display welcome message
  cout <<"Welcome to the Fish Tank Computer" << endl;
  cout <<"Enter the following information:" << endl;

 

//user inputs length
  cout <<"Please enter the length of the tank in feet" << endl;
  cin >> length;

 

//user inputs whether fish are present
  cout <<"Are fish present (1 - yes, 0 - no)?" << endl;
  cin >> areFishPresent;

 

//make width and height calculations
  width = length * (1.0/4.0);
  height_ft = length * (2.0/3.0);

 

//make water volume calculations
  if (areFishPresent == 1){
    water_volume = tank_volume - 2;
  }
  else{
    water_volume = tank_volume;
  }

 

//determine number of fish the tank can hold
  fish1 = water_volume / 25;

 

//determine amount of nuclear waste required
  height_in = height_ft / 12;
  waste_mass = 11 / height_in;

 

//output measurements
  cout <<"Your tank dimensions are:" << endl;
  cout << "length" << length << "ft" << endl;
  cout << "width" <<  width << "ft" << endl;
  cout << "height" << height_ft << "ft" << endl;
  cout << "tank cap" << tank_volume << "gals" << endl;
  cout << "water" << water_volume << "gals" << endl;
  cout << "waste" << waste_mass << "rads" << endl;
  cout << "Your tank will hold:" << fish1 << "fish." << endl;
  cout << "Thank you for using the Fish Tank Computer." << endl;

  return 0;
}

 

[79wjd]

Just now, multitasker451 said:

using namespace std;

int main()
{
  int length, width, height_ft, height_in, areFishPresent, fish1;
  float tank_volume, water_volume, waste_mass;
 

  //display welcome message
  cout <<"Welcome to the Fish Tank Computer" << endl;
  cout <<"Enter the following information:" << endl;

  //user inputs length
  cout <<"Please enter the length of the tank in feet" << endl;
  cin >> length;

  //user inputs whether fish are present
  cout <<"Are fish present (1 - yes, 0 - no)?" << endl;
  cin >> areFishPresent;

  //make width and height calculations
  width = length * (1.0/4.0);
  height_ft = length * (2.0/3.0);

  //make water volume calculations
  if (areFishPresent == 1){
    water_volume = tank_volume - 2;
  }
  else{
    water_volume = tank_volume;
  }

  //determine number of fish the tank can hold
  fish1 = water_volume / 25;

  //determine amount of nuclear waste required
  height_in = height_ft / 12;
  waste_mass = 11 / height_in;

  //output measurements
  cout <<"Your tank dimensions are:" << endl;
  cout << "length" << length << "ft" << endl;
  cout << "width" <<  width << "ft" << endl;
  cout << "height" << height_ft << "ft" << endl;
  cout << "tank cap" << tank_volume << "gals" << endl;
  cout << "water" << water_volume << "gals" << endl;
  cout << "waste" << waste_mass << "rads" << endl;
  cout << "Your tank will hold:" << fish1 << "fish." << endl;
  cout << "Thank you for using the Fish Tank Computer." << endl;

  return 0;
}

 

What happens if you run it? (p.s. magic numbers are bad style). 

[scottyseng]

2 minutes ago, multitasker451 said:

  int length;
  int width;
  int height_ft;
  int height_in;

  width = length * (1.0/4.0);
  height_ft = length * (2.0/3.0);

width and height_ft should be float

[79wjd]

Just now, scottyseng said:

width and height_ft should be float

They'll just get truncated, that won't break anything.

[scottyseng]

Just now, djdwosk97 said:

They'll just get truncated, that won't break anything.

Ah, forgot about that. Yeah, I'm still trying to see what else would break in this code.