if loop problems

bco1109 · #1 11-Oct-2005, 11:50

I am having problems with the following progamany ideas?

CPP / C++ / C Code:

void main()

{
	 int choice; 
	 int a,b,c,d=0;
	 int is_prime(int n);
     float ctemp,ftemp ;
  	 char Type;	                        
	 cout << "Please enter 'c' to convert temprature between celcius or farenhheit\n";	                
	 cout << "Please enter 'p'' for finding a prime number\n";	                 
	 cout << "Please enter 'q'' to quit\n";	                 
	 cin>> Type; 
	 while (Type !='q' ||'Q'){
		
			if(Type =='c'|| 'C')  
			{
				cout << "1.Celsius to Fahrenheit" << endl;
				cout << "2.Fahrenheit to Celsius" << endl;
				cout << "Choose either 1 or 2 : " << endl;
				cin>>choice;
				if (choice==1)
				{
					cout << "Enter the temperature in Celsius : " << endl;
					cin>>ctemp;
					ftemp=(1.8*ctemp)+32;
					cout << "Temperature in Fahrenheit = " << ftemp << endl;
				}
				else
				{
					cout << "Enter the temperature in Fahrenheit : " << endl;
					cin>>ftemp;
					ctemp=(ftemp-32)/1.8;
					cout << "Temperature in Celsius = " << ctemp << endl;
				}
			}
			if(Type == 'p' || 'P')                                                      			
			{
				printf ("\n Enter a Number : ");
				scanf ("%d",&a);
				for (b=2;b<a;b++)
				{
					c=a%b;
					if (c==0)
					{
						d=1;
						break;
					}
				}
			     switch (d)
				{
				case 1:
				printf ("\n The Numer is NOT a Prime Number");
				break;
				default:
				printf ("\n The Number is a Prime Number ");
				}
			}
                                        
			else 	
				cout << "invalid entry" << endl;                       
	        }                                                       
                                                               
}

bco1109 · #2 11-Oct-2005, 12:01

The compiler is c++ and here are the program requirements.

rite a C++ program that shows the following menu:

P[rime] C[onversion] Q[quit]

• If you select "P or p" You should invoke a user-defined function, int prime (void) to prompt the user to enter a number and determine whether or not the number is a prime number. Print the number in function main (). (Hint: you may use modulus, % operator)

• If the user select "C or c" You should invoke a user-defined function void convert (void) to convert from Fahrenheit to Celsius or from Celsius to Fahrenheit. In this function prompt the user for the following submenu:

1. Convert from Fahrenheit to Celsius
2. Convert from Celsius to Fahrenheit

The user should choose one of the options. Then prompt the user for appropriate temperature and then display corresponding temperature. Use the conversion equations below:

F = (9/5)C + 32
C = (5/9) (F-32)

• If the user selects “q or Q” then your program should terminate.

Kacyndra · #3 11-Oct-2005, 12:04

try this

CPP / C++ / C Code:

if((Type =='c')|| (Type == 'C'))

Paramesh · #4 11-Oct-2005, 12:30

Hi bco

Welcome to the GID Forums.

If is not a Loop. for, while, do while are loops. If is just a statement to check whether the condition is true or not.

The main error in your program is that you should put the cin>>Type inside your loop. you should get the input from the user everytime isnt it?

You have to use functions as you said.

The function declaration should be of this type:

CPP / C++ / C Code:

CPP / C++ / C Code:

return-type function-name(parameter list)
{
declarations and statements;
return expression;
}

The return-type specifies the type of data that the function returns. The parameter list is a comma-separated list of variable names and their associated types that receive the values of the arguments when the function is called . All function parameters must be declared individually, each including both the type and name. That is, the parameter declaration list for a function takes this general form:
f(type varname1, type varname2, . . . , type varnameN)

For example consider your prime number function.
it should be like this:

CPP / C++ / C Code:

int  prime(void)
{
//code to find whether a number is a prime number or not

return x; //where x is return value
}

You can construct a similar function for Celsius/fanrenheit conversion.

then in your main program use a do while loop so that you get input from the user atleast once.
You may use this method:

CPP / C++ / C Code:

do
{
//get input;
//use if or switch statements
//use the functions accordingly
} while( Type != 'q'  || Type != 'Q' );

and your

CPP / C++ / C Code:

switch (d)
{
case 1:
printf ("\n The Numer is NOT a Prime Number");
break;
default:
printf ("\n The Number is a Prime Number ");
}

can simplified by using if and else statement because d can be only 1 or 0.

Regards,
Paramesh.

bco1109 · #5 11-Oct-2005, 14:15

This is what I have so far. I am sure I am missing something however making progress.

CPP / C++ / C Code:

int main(void) 
{
	 int choice; 
	 int a,b,c,d=0;
	 int is_prime(int n);
	 tempconv;
	 int prime;
     float ctemp,ftemp ;
  	 char Type;	                        
	 
	do
	 {
		cout << "Please enter 'c' to convert temprature between celcius or farenhheit\n";	                
		cout << "Please enter 'p'' for finding a prime number\n";	                 
		cout << "Please enter 'q'' to quit\n";	                 
		 cin>> Type; 
		
			if((Type =='c')||(Type =='C')) 
		int tempconv(void)
			{
				cout << "1.Celsius to Fahrenheit" << endl;
				cout << "2.Fahrenheit to Celsius" << endl;
				cout << "Choose either 1 or 2 : " << endl;
				cin>>choice;
				if (choice==1)
				{
					cout << "Enter the temperature in Celsius : " << endl;
					cin>>ctemp;
					ftemp=(1.8*ctemp)+32;
					cout << "Temperature in Fahrenheit = " << ftemp << endl;
				}
				else
				{
					cout << "Enter the temperature in Fahrenheit : " << endl;
					cin>>ftemp;
					ctemp=(ftemp-32)/1.8;
					cout << "Temperature in Celsius = " << ctemp << endl;
				}
				returntemp;
			}
			if((Type == 'p')||(Type== 'P'))   
      int prime (void)
			{
				printf ("\n Enter a Number : ");
				scanf ("%d",&a);
				for (b=2;b<a;b++)
				{
					c=a%b;
					if (c==0)
					{
						d=1;
						break;
					}
				}
			     switch (d)
				{
				case 1:
				printf ("\n The Numer is NOT a Prime Number");
				break;
				default:
				printf ("\n The Number is a Prime Number ");
				}
		return printf
			}
                                        
			else 	
				cout << "invalid entry" << endl;                       
	        } 
while ((Type !='q')||(Type!='Q')) 
{
	 return (main);                                                      
}

bco1109 · #6 11-Oct-2005, 15:17

I have the program working however I have a few problems.

1. When i quit the progam it continues to loop invalid entry.

2. when I check for a prime number, once I enter a non prime number it will not detect the prime number anymore.

Below is the C++ code I have so far.

CPP / C++ / C Code:

#include <iostream.h>
#include <math.h>
#include<stdio.h>
#include<conio.h>
#include<assert.h>



//function main begins program execution
int main(void) 
{
	 int choice; 
	 int a,b,c,d=0;
	 int is_prime(int n);
     float ctemp,ftemp ;
  	 char Type;	                        
	 cout << "Please enter 'c' to convert temprature between celcius or farenhheit\n";	                
	 cout << "Please enter 'p'' for finding a prime number\n";	                 
	 cout << "Please enter 'q'' to quit\n";	                 
	 cin>> Type; 
	 while ((Type !='q')||(Type!='Q')){
		
			if((Type =='c')||(Type =='C'))  
			{
				cout << "1.Celsius to Fahrenheit" << endl;
				cout << "2.Fahrenheit to Celsius" << endl;
				cout << "Choose either 1 or 2 : " << endl;
				cin>>choice;
				if (choice==1)
				{
					cout << "Enter the temperature in Celsius : " << endl;
					cin>>ctemp;
					ftemp=(1.8*ctemp)+32;
					cout << "Temperature in Fahrenheit = " << ftemp << endl;
				}
				else
				{
					cout << "Enter the temperature in Fahrenheit : " << endl;
					cin>>ftemp;
					ctemp=(ftemp-32)/1.8;
					cout << "Temperature in Celsius = " << ctemp << endl;
				}
			}
			if((Type == 'p')||(Type== 'P'))                                                      			
			{
				printf ("\n Enter a Number : ");
				scanf ("%d",&a);
				for (b=2;b<a;b++)
				{
					c=a%b;
					if (c==0)
					{
						d=1;
						break;
					}
				}
			     switch (d)
				{
				case 1:
				printf ("\n The Numer is NOT a Prime Number");
				break;
				default:
				printf ("\n The Number is a Prime Number ");
				}
			}
                                        
			else 	
				cout << "invalid entry" << endl;                       
	        }  
	 return 0;                                                      
}

Sokar · #7 11-Oct-2005, 16:35

Quote:

Originally Posted by bco1109

I have the program working however I have a few problems.

1. When i quit the progam it continues to loop invalid entry.

This,

CPP / C++ / C Code:

while((Type !='q')||(Type!='Q'))

when you use "or"(||) only one has to be true for the whole statement to be true.
But,

CPP / C++ / C Code:

while((Type !='q')&&(Type!='Q'))

"and"(&&) they both must be true for the statement to be true. Since "Type" cannot be both 'q' and 'Q' at the same time when it is lower or upper case it will fail.

Quote:

Originally Posted by bco1109

2. when I check for a prime number, once I enter a non prime number it will not detect the prime number anymore.

I see this,

CPP / C++ / C Code:

if(c==0)
{
	d=1;
	break;
}

But I do not see where you ever change the value to anything else. It is stuck with the value 1.

bco1109 · #8 11-Oct-2005, 16:51

Should i use d=1++

Sokar · #9 11-Oct-2005, 17:10

Quote:

Originally Posted by bco1109

Should i use d=1++

I am sure that will not compile. You can only change lvalues and "1" in not a lvalue.
Some information on "lvalue"
http://cplus.about.com/od/cprogrammi...def_lvalue.htm

You might just try reseting "d" to the original value if you do not need it to keep the value "1".

CPP / C++ / C Code:

case 1:
	printf ("\n The Numer is NOT a Prime Number");
	d=0;
	break;

bco1109 · #10 11-Oct-2005, 18:38

Thanks for the help. everything is looking good exept fot the termination of the program. If i add a break then it will not loop back.

CPP / C++ / C Code:

#include <iostream.h>
#include <math.h>
#include<stdio.h>
#include<conio.h>
#include<assert.h>



//function main begins program execution
int main(void) 
{																					//
	 int choice;																	//
	 int a,b,c,d=0;																	//
	 int is_prime(int n);															//
     float ctemp,ftemp ;															//	
  	 char Type;																		//
	 cout << "Please enter 'c' to convert temprature between celcius or farenhheit\n";	//                
	 cout << "Please enter 'p'' for finding a prime number\n";						//	
	 cout << "Please enter 'q'' to quit\n";											//
	 cin>> Type;																	//
	 do																				//
	 {																				//
																					//
			if((Type =='c')||(Type =='C'))											//
			{																		//
				cout << "1.Celsius to Fahrenheit" << endl;							//	
				cout << "2.Fahrenheit to Celsius" << endl;							//
				cout << "Choose either 1 or 2 : " << endl;							//
				cin>>choice;														//
				if (choice==1)														//
				{																	//
					cout << "Enter the temperature in Celsius : " << endl;			//	
					cin>>ctemp;														//
					ftemp=(1.8*ctemp)+32;											//
					cout << "Temperature in Fahrenheit = " << ftemp << endl;		//
				}																	//
				else if (choice ==2)												//
				{																	//
					cout << "Enter the temperature in Fahrenheit : " << endl;		//
					cin>>ftemp;														//
					ctemp=(ftemp-32)/1.8;											//
					cout << "Temperature in Celsius = " << ctemp << endl;			//
				}																	//
				else																//
				{																	//
					cout <<"Invalid entry";											//
				}																	//
			}																		//
			if((Type == 'p')||(Type== 'P'))                                         //           			
			{																		//
				printf ("\n Enter a Number : ");									//
				scanf ("%d",&a);													//
				for (b=2;b<a;b++)													//
				{																	//
					c=a%b;															//
					if (c==0)														//
					{																//
						d=1;														//
						break;														//
					}																//		
				}																	//end of innner loop
			     switch (d)															//begining of switch
				{																	//begining of switch
				case 1:																//case if not prime
				printf ("\n The Numer is NOT a Prime Number");                      //print the number is not prime
				d=0;
				break;
				default:															//case if prime number
				printf ("\n The Number is a Prime Number ");							//print the number is prime
				break;																//end of switch
				}																	//end of switch
			}																		//end of inner loop
			else 																	//break out of the loop
				cout << "invalid entry" << endl;								  //print invalid entry
			break;                                  

	  	  
	 }
																	//end of main loop
	 while ((Type !='q')&&(Type!='Q'));											    //While function to quit program
	 cout << "To terminate program" << endl; 


	 return 0;																	//indicate the program ended sucessfully
}																				    //end main function

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