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C++ variable types precision?
I'm writing a program for C++ that finds a square root approximation. Here's the program:
#include <cstdio>
#include <cstdlib>
#include <iostream>
using namespace std;
int main(int nNumberofArgs, char* pszArgs[])
{
cout << "Radicand?" << endl;
int radicand;
cin >> radicand;
cout << "Guess?" << endl;
double guess;
cin >> guess;
double error;
error = radicand-(guess*guess);
while(-.000001>error>.000001);
{ guess=(.5*(guess + radicand/guess));
error = radicand - (guess*guess);
}
cout << "The square root approximation of " << radicand << " is " << guess << endl;
cout << guess << " squared is " << guess*guess <<endl;
system("PAUSE");
return 0;
}
_____________________________
The problem is that the answer it returns is only 5 decimal points precision. I specified that it's a double. What's up with that?
6 Answers
- PfoLv 71 decade agoFavourite answer
while(-.000001>error>.000001);
That's a problem. First, you can't do this: -.000001>error>.000001. At least not on most compilers, also you have a semicolon after that loop, so the loop wouldn't do anything. Try this:
while (abs(error) > 0.00001)
{
// code
}
Your while loop isn't executing, and the body will execute only once.
* include math.h for the abs (absolute value) function
- 1 decade ago
6 is default for double, if you need more you have to specify it
this example would give you 10 decimal point precision you insert it before your cout statements at the end
like this:
cout. precision(11);
cout << "The square root approximation of " << radicand << " is " << guess << endl;
cout << guess << " squared is " << guess*guess << endl;
should give you 10 decimal places, you can edit the number as needed
hope that helps
- ErikaLv 44 years ago
For int and lengthy, you're waiting to favor to seem on the record "limits.h". you do now no longer favor to #comprise it as you'll do with <stdio.h> or <stdlib.h>, you want to open it in an editor and bypass to the Numerical Limits section. that allow you to carry close the major significant integer fee that is valid and from that, you'll get the variety of bytes of the variable. in case you want to code, you're waiting to write down a application which will #comprise <limits.h> and which will print the barriers.
- Paul WLv 51 decade ago
Use the printf function for output and you can specify how many decimal points precision you want displayed.
- 1 decade ago
Above guy is correct!
here is the way:
change code that cout an "guess" with printf(), with format %[flags][width] [.precision]
the flags is "d", so the code become:
printf("%4.8d", guess);
