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Simple question about # of digits.

crystalgem (86)
I'm modifying a project that I'm working on to give the user more control.
One of the parts of my project involves using pi (3.1415926535 etc).
I would like to be able to set pi equal to a huge number, then give the user the opportunity to express how many decimals they would like pi used to.

Below is a dumbed down version of my project involving just the pi code.

If anyone could help me figure out how to do this, I'd be grateful! 


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#include "stdafx.h"
#include <iostream>
using namespace std; 
double piChoice(double);
double piEditor(double);

int main(){
   double pi = 3.14159;
   
   pi = piChoice(pi); 
   piEditor(pi);

return 0;
}

double piChoice(double pi){
	int decimal;

	cout << "Pi can be calculated from 2 to 5 decimal places." << endl;
	cout << "How many decimal places would you like it calculated to: "<< endl; 
	cin  >> decimal;
    while (decimal < 2 || decimal > 5){
	   cout << "Please chose a number between 2 and 5." << endl; 
	   cout << "How many decimal places would you like pi calculated to: " << endl; 
	   cin  >> decimal;
	}

    // Some sort of code to set pi to extend out "decimal" number of digits.  

	return pi;
} 

double piEditor(double pi){

// This is where I will be using the modified pi. 
// For simplicity's sake, I'll just stick an output here
// instead of using the 6 page code I have.

   cout << "Your pi equals: " << pi << endl;

   return 0;
}
closed account (3TXyhbRD)
Implement a fraction number (retains counter and denominator). When returning the number as float use an array of ints so you don't need to worry about float or double type size restrictions.
crystalgem (86)
I don't think fractions are really needed in this.

I figured out one way to accomplish my goal, but it's kind of... long winded...


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#include "stdafx.h"
#include <iostream>
#include <iomanip>

using namespace std; 
int piChoice();
int piEditor(int);

int main(){
   double pi = 0;
   
   int dec = piChoice(); 
   piEditor(dec);

return 0;
}

int piChoice(){
	int decimal;

	cout << "Pi can be calculated from 2 to 14 decimal places." << endl;
	cout << "How many decimal places would you like it calculated to: "<< endl; 
	cin  >> decimal;
    while (decimal < 2 || decimal > 14){
	   cout << "Please chose a number between 2 and 14." << endl; 
	   cout << "How many decimal places would you like pi calculated to: " << endl; 
	   cin  >> decimal;
	}

	return decimal;
} 

int piEditor(int dec){
    double pi;

        if      (dec ==  1)
            pi = 3.14;
	else if (dec ==  3)
            pi = 3.141;
	else if (dec ==  4)
	    pi = 3.1415;
	else if (dec ==  5)
		pi = 3.14159;
	else if (dec ==  6)
		pi = 3.141592;
	else if (dec ==  7)
		pi = 3.1415926;
	else if (dec ==  8)
		pi = 3.14159265;
	else if (dec ==  9)
		pi = 3.141592653;
	else if (dec == 10)
		pi = 3.1415926535;
	else if (dec == 11)
		pi = 3.14159265358;
	else if (dec == 12)
		pi = 3.141592653589;
	else if (dec == 13)
		pi = 3.1415926535897;
	else if (dec == 14)
		pi = 3.14159265358979;

   cout << setprecision(15) << pi << endl;

   cout << "Your pi equals: " << pi << " with " << dec << " decimals. " << endl;

   return 0;
}
crystalgem (86)
Any other ideas to shorten this?
cire (8284)
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int piEditor(int dec){
    double pi = 3.14159265358979 ;

	if ( dec <= 1 )
		dec = 2 ;

   cout << "Your pi equals: " << setprecision(dec+1) << pi << " with " << dec << " decimals. " << endl;

   return 0;
}


You don't round correctly in your function. piEditor seems like a very inaccurate name -- you aren't editing anything. So does the wording of the prompt since you aren't actually calculating pi. I also wonder why piEditor return an int.
Last edited on
crystalgem (86)
Because this is just a dummy program representing a single problem in a 6 page project I'm working on.
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