Limiting input values

**Creatlv3** · 02-11-2010

I am trying to limit my program to only accept four possible numbers, 1,2,3 and 4.
the current working code i have is

Code:

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
	double x; //choice
	double r; //radius
	double a; //volume
	double b; //surface area
	double c; //area of a circle
	double h; //height
	double l; //length
	double w; //width
	
	do
	{
	cout<< "What shape would you like?"<<endl;
	cout<< "1) Sphere"<< endl;
	cout<< "2) Cone"<< endl;
	cout<< "3) Rectangular Prism"<< endl;
	cout<< "4) Cylinder"<< endl;
	cout<< "Choice is ";
	cin>>x;
	}
	while (x<1||x>4);//only want numbers 1, 2, 3, or 4

When i use the code

Code:

while (x<1||1<x<2||2<x<3||3<x<4||x>4)

it returns me to the input command every time even if i input 1,2,3 or 4

any help is useful
thx

**yaya** · 02-12-2010

It should be the other way around and use AND:
while ( x >= 1 && x <= 4 )

**Creatlv3** · 02-12-2010

wont that make the loop run every time i input a value between 1 and 4 instead of excluding all the values outside 1 and 4?
I want the program to run that section every time i don't input a value of 1, 2, 3 or 4

**yaya** · 02-12-2010

Oops, sorry. Wasn't thinking. In that case, all you need is the &&. So:
while ( x < 1 && x > 4 )

**iMalc** · 02-12-2010

it returns me to the input command every time even if i input 1,2,3 or 4

No it doesn't! The originally posted code with

Code:

	while (x<1||x>4);//only want numbers 1, 2, 3, or 4

is already correct! The loop is exited if you type 1, 2, 3, or 4. If you type a number less than 1 or greater than 4 then the loop is repeated. That is what you have written.

Did you want it to do something else besides ask for the input again when it was out of range?

**iMalc** · 02-12-2010

Originally Posted by yaya

Oops, sorry. Wasn't thinking. In that case, all you need is the &&. So:
while ( x < 1 && x > 4 )

How many numbers do you know that are both less than one AND greater than four?!?!

**yaya** · 02-12-2010

Haha, damn, I'm having a bad day. I should sleep more before I start answering these.

**laserlight** · 02-12-2010

By the way, instead of:

Code:

double x; //choice
double r; //radius
double a; //volume
double b; //surface area
double c; //area of a circle
double h; //height
double l; //length
double w; //width

You might as well write:

Code:

double choice;
double radius;
double volume;
double surface_area;
double circle_area;
double height;
double length;
double width;

Though choice probably should be of an integer type.

**_Mike** · 02-12-2010

Originally Posted by iMalc

How many numbers do you know that are both less than one AND greater than four?!?!

Code:

int x = -1;
while (x < 1 && (unsigned int)x > 4)

Btw, don't take this seriously. It was more of a joke on how you can make even the simplest bit of code really confusing

**Creatlv3** · 02-12-2010

Originally Posted by _Mike

Code:

int x = -1;
while (x < 1 && (unsigned int)x > 4)

Btw, don't take this seriously. It was more of a joke on how you can make even the simplest bit of code really confusing

Don't worry I'm not going to take it seriously. I haven't yet read up on using the "int" command or yet been taught how to use it in class yet, so you've confused me from the very beginning

@Laserlight i prefer to use single character variables, since its easier to use them in the math equations later on in the program.

and im just going to keep my code the way it is now since trying to figure out a way for it to only accept the values 1, 2, 3 or 4 at this point in time for me is beyond my capabilities. Thank you all for helping/trying to help me with my little conundrum

**laserlight** · 02-12-2010

Originally Posted by Creatlv3

@Laserlight i prefer to use single character variables, since its easier to use them in the math equations later on in the program.

Resist the temptation. Code should be readable, not just "writable".

**Creatlv3** · 02-12-2010

Tis be a strong temptation with 10 years of math drilling single variables into my head, eventually i will probably be able to break it but for the time being im going to use appropriate letters to keep things simple. However "a" for volume and "b" for surface area definitely not the best choices.

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