Formatting numbers with a given number of decimal places

[scan87]

Can somone please, please give me the solution for the following problem. I need to submit it on Monday.

Write a global function called format, which formats numbers with a given number of decimal places. The function accepts a compulsory first argument of type double (the number to be formatted) and a second optional argument of type integer (the number of decimal places) and returns a string object containing the formatted text. If the second argument is missing, the formatting should assume two (2) decimal places. No user-interaction code is allowed in this function.
Write the main function shown below as a test for your function.

#include<iostream.h>
int main()
{
  double n1 = 1.24, n2 = 1.25, n3 = 3456.67953;
  cout << "'" << format( n1, 1 ) << "'" << endl;
  cout << "'" << format( n2, 1 ) << "'" << endl;
  cout << "'" << format( n3 )    << "'" << endl;
  cout << "'" << format( n3, 3 ) << "'" << endl;
  return 0;
}
 

If the format function is written correctly, the above test should output
'1.2'
'1.3'
'3456.68'
'3456.680'

Thanxxxx in advance.

[sicarie]

Can somone please, please give me the solution for the following problem. I need to submit it on Monday.

Write a global function called format, which formats numbers with a given number of decimal places. The function accepts a compulsory first argument of type double (the number to be formatted) and a second optional argument of type integer (the number of decimal places) and returns a string object containing the formatted text. If the second argument is missing, the formatting should assume two (2) decimal places. No user-interaction code is allowed in this function.
Write the main function shown below as a test for your function.

#include<iostream.h>
int main()
{
  double n1 = 1.24, n2 = 1.25, n3 = 3456.67953;
  cout << "'" << format( n1, 1 ) << "'" << endl;
  cout << "'" << format( n2, 1 ) << "'" << endl;
  cout << "'" << format( n3 )    << "'" << endl;
  cout << "'" << format( n3, 3 ) << "'" << endl;
  return 0;
}
 

If the format function is written correctly, the above test should output
'1.2'
'1.3'
'3456.68'
'3456.680'

Thanxxxx in advance.

What did you get when you tried this? Can you post your code?

[scan87]

I wrote the global function but I tried to compile it the program is giving errors and the full program code is as follows:

#include <iostream.h>
#include<math.h>
double format(double,int);    // function prototype
int main()
{
      double n1 = 1.24, n2 = 1.25, n3 = 3456.67953;
      cout<<"'"<<format(n1,1)<<"'"<<endl;
      cout<<"'"<<format(n2,1)<< "'"<<endl;
      cout<<"'"<<format(n3)<< "'"<<endl;
      cout<<"'"<<format(n3,3)<< "'"<<endl;
      return 0;
}
 
double format(double val,int n)
{
    double mult=pow(10,n);
    long int ans=(val*mult);
    double res=ans/mult;
    return res;
}
 

And the errors are:
format.cpp: In function âint main()â:
format.cpp:7: error: âformatâ was not declared in this scope
format.cpp: In function âdouble format(double, int)â:
format.cpp:15: error: âpowâ was not declared in this scope
format.cpp:16: warning: converting to âlong intâ from âdoubleâ

[sicarie]

Are you writing this in C or C++?

[scan87]

I am writing this program in C++.

[sicarie]

Updated minor bits of the code for readability.

#include <iostream>
#include<math.h>
using namespace std;
double format(double val, int n);       // function prototype
int main()
{
        double n1 = 1.24, n2 = 1.25, n3 = 3456.67953;
        cout<<"'"<<format(n1,1)<<"'"<<endl;
        cout<<"'"<<format(n2,1)<< "'"<<endl;
        cout<<"'"<<format(n3)<< "'"<<endl;
        cout<<"'"<<format(n3,3)<< "'"<<endl;
        return 0;
}
 
double format(double val,int n)
{
        double mult, ans, res;
        mult=pow(10,n);
        ans=(val*mult);
        res=ans/mult;
        return res;
}
 
 

So, one thing I see is line ten when you send format only n3. Your function has to pass this test, right? It is one your teacher wrote? Because your format() does not handle this.

[sicarie]

And what I meant to ask was: can you pass it 0, or does it have to conform strictly to that test file?

[scan87]

Ok so what should I do now?

[scan87]

Its still giving errors.

[sicarie]

Its still giving errors.

Can you explain to me what each line of your format function does? (To make sure the algorithm to set the decimal precision is correct).

[RedSon]

 
#include <iostream>
#include<math.h>
using namespace std;
double format(double val, int n);       // function prototype
int main()
{
    double n1 = 1.24, n2 = 1.25, n3 = 3456.67953;
    cout << "'" << format(n1,1) << "'" << endl;
    cout << "'" << format(n2,1) << "'" << endl;
    cout << "'" << format(n3,0) << "'" << endl;
    cout << "'" << format(n3,3) << "'" << endl;
    return 0;
}
 
double format(double val,int n)
{
    double mult, ans, res;
    mult = ::pow(val, n);
    ans = (val*mult);
    res = ans/mult;
    return res;
}
 

I fixed some stuff, and now it compiles. See if this works.

[scan87]

Thank you very much its working.

[sicarie]

Thank you very much its working.

Thanks RedSon.

[scan87]

Can you please tell me what you did in the format( ) part of the program.

[RedSon]

Can you please tell me what you did in the format( ) part of the program.

I added the scope resolution operator before pow the "::" and also changed your method call to have two arguments.

[Ganon11]

The function accepts a compulsory first argument of type double (the number to be formatted) and a second optional argument of type integer (the number of decimal places) and returns a string object containing the formatted text. If the second argument is missing, the formatting should assume two (2) decimal places.

So far, people have changed your 3rd format( ) call to be format(n3, 0), but according to the assignment, the second argument is optional - thus, format(n3) should function. In order for this to work, in your function prototype, you must declare a default value for n, like this:

double format(double val, int n = 2);

If no value is given for n in the call, then then program will assume that a 2 was passed. If a value is provided for n, then the program ignores the n = 2 and takes the given n.

[sicarie]

So far, people have changed your 3rd format( ) call to be format(n3, 0), but according to the assignment, the second argument is optional - thus, format(n3) should function. In order for this to work, in your function prototype, you must declare a default value for n, like this:

double format(double val, int n = 2);

If no value is given for n in the call, then then program will assume that a 2 was passed. If a value is provided for n, then the program ignores the n = 2 and takes the given n.

Thank you Ganon. I knew there was a way to do it, and have been trying to figure it out!

[RRick]

It appears that there is some kind of conflict between iostream and format. I'm not sure what it is, but gnu doesn't like it, either.

Try changing the name of format to something really different (like xxxformat) and see if that particular error goes away.