Programming Forums > Application Development > C++

Easter Bunny · Apr 5th, 2005, 10:11 AM

g'day, i'm currently studying through correspondence and one of the questions for an assignment has to do with changing pounds to kilo's, or yards to meters or something. that's fine, i can do that, but then it say round up to 2 decimals. i searched the site and quickly googled it, but didn't find anything that made sense. i looked in the books they gave me + the book i got from my mom's library, but that didn't help, because i couldn't find anything.

is there something in c++ that lets you set a standard "look" for your numbers like java's DecimalFormat? or do i have to stay up all night and drink lots of (strong) coffee and make my own function thingy that will look at the numbers after the "." and ceil() or floor() or something like that?

oh, i'm very new new to c++. started studying this year, so you can't laugh at me and tell all your friends that there's actually a dude who doesn't know how to implement rounding in c++.

thanks for the help(in advance of course)and for those who help me, you should pop round sometime and we can have a braai(bbq in english)and talk about integers, strings, etc. it'll be fun.�

spydoor · Apr 5th, 2005, 11:20 AM

(Toggle Plain Text)

cout << fixed << setprecision(2) << value;

tempest · Apr 5th, 2005, 5:26 PM

(Toggle Plain Text)

float round(float val, int prec) {
  	val *= (10^prec);
  	val = (int)val;
  	return val/(float)prec;
  }

Easter Bunny · May 3rd, 2005, 10:20 AM

here you go, this is what i've got. it works on some numbers, but not on all. i end up being out by 0.000000000000...00001 sometimes. sat for hours trying to work something out, but not getting there.

the Temp = ceil( f ); part works for the first part of the assignment's test data, but on the second i'm over by 0.000001, then it rounds up and then i'm over by 0.01 or something. stole the recursive function from another post here(thanks dude!

). if i take out the ceil( f ) bit, then on the first bit of data i'm under by 0.01 or so.

i'm close to having a hernia.

(Toggle Plain Text)

int exponent( int Num, int Exp )
{
    if ( Exp == 0 )
        return 1;
    return ( Num * ( exponent( Num, Exp-1 ) ) );
}

float rounding( float f, int Exp )
{
    int Temp;
    int Div = exponent( 10, Exp );
    f *= Div;
    
    Temp = ceil( f );
    
    f = (int)Temp;
    f /= Div;
    return f;
}

thanks for the help(in advance of course).

Easter Bunny · May 3rd, 2005, 10:21 AM

when i use

(Toggle Plain Text)

cout << fixed << setprecision(2) << value;

do i have to include something special, because it doesn't work when i compile.

BaroN NighT · May 3rd, 2005, 10:41 AM

Yes you do :

#include <iomanip>

then you can use setprecision(n). n is the number of decimal places you want the program to output.

Easter Bunny · May 6th, 2005, 7:11 AM

ok, so i included iomanip, but it still says "'setprecision' undeclared (first use this function)".

i'd rather ask a question and look stupid, than be stupid forever, so here goes...

(Toggle Plain Text)

cout << fixed << setprecision(2) << value;

what would it look like in my program? this:

(Toggle Plain Text)

cout << fixed << setprecision(2) << Arr[i];

Arr[i] is an array of floats.

i do feel slightly stupid now, but i'm sure it's not gonna last for long... and think of all the other people you're helping who are too affraid to ask and blah blah blah...

thanks.

spydoor · May 6th, 2005, 7:56 AM

use namespace std , or fully qualify

(Toggle Plain Text)

#include <iostream>
#include <iomanip>
using namespace std; // if you don't do this you have to fully qualify cout, fixed, setprecision .....

int main () {
  double f =3.14159;
  cout << fixed << setprecision (2) << f << endl; 
  std::cout << std::fixed << std::setprecision (4) << f << std::endl;
  return 0;
}

Easter Bunny · May 6th, 2005, 8:38 AM

this is the whole thing so far. first two functions i spent hours on, but it doesn't work 100%.

(Toggle Plain Text)

//assignment 3 --> question 1a
#include <iostream>
#inclide <iomanip>
using namespace std;

int exponent( int Num, int Exp )
{
    if ( Exp == 0 )
        return 1;
    return ( Num * ( exponent( Num, Exp-1 ) ) );
}

float rounding( float f, int Exp )
{
    int Temp;
    int Div = exponent( 10, Exp );
    f *= Div;
    //this worked for the first half of the test data, but second half it's out by a bit
//    Temp = ceil( f );
    
    f = (int)Temp;
    f /= Div;
    return f;
}

void getInput( float Arr[] )
{
    for ( int i = 0 ; i < 20 ; i++ )
    {
        cin >> Arr[i];
    }
}

void getDifference( float Arr1[], float Arr2[], float Arr3[] )
{
    for ( int i = 0 ; i < 20 ; i++ )
    {
        Arr3[i] = Arr2[i] - Arr1[i];
    }
}

void displayResults( string Message, float Arr[], int Round )
{
    cout << "The differences in " << Message << " : " << endl << endl << endl;
    
    for ( int i = 0 ; i < 20 ; i++ )
    {
        if ( Arr[i] < 0 )
        {
        //    cout << i << " -> " << " down" << endl;
            cout << fixed << setprecision(2) << -Arr[i];
        }
        else
        {
            if ( Arr[i] > 0 )
            {
                //this is my attempts at the rounding thing with those functions
                cout << i << " -> " << rounding( Arr[i], Round ) << " up" << endl;
            }
            else
            {
                cout << i << " -> stayed the same" << endl;
            }
        }
    }
    
    cout << endl;
}

int main()
{
    float Info2004[20], Info2005[20], Difference[20];
    string Message;
    
    cout << "Enter April 2004 lengths : " << endl;
    getInput( Info2004 );
    
    cout << "Enter April 2005 lengths : " << endl;
    getInput( Info2005 );
    
    getDifference( Info2004, Info2005, Difference );
    Message = "weights";
    displayResults( Message, Difference, 2 );

//*******************

    cout << "Enter April 2004 weights : " << endl;
    getInput( Info2004 );
    
    cout << "Enter April 2005 weights : " << endl;
    getInput( Info2005 );
    
    getDifference( Info2004, Info2005, Difference );
    Message = "lengths";
    displayResults( Message, Difference, 1 );
    
    system( "PAUSE" );
    return 0;
}

//assignment 3 --> question 1a
#include <iostream>
#inclide <iomanip>
using namespace std;

int exponent( int Num, int Exp )
{
    if ( Exp == 0 )
        return 1;
    return ( Num * ( exponent( Num, Exp-1 ) ) );
}

float rounding( float f, int Exp )
{
    int Temp;
    int Div = exponent( 10, Exp );
    f *= Div;
    //this worked for the first half of the test data, but second half it's out by a bit
//    Temp = ceil( f );
    
    f = (int)Temp;
    f /= Div;
    return f;
}

void getInput( float Arr[] )
{
    for ( int i = 0 ; i < 20 ; i++ )
    {
        cin >> Arr[i];
    }
}

void getDifference( float Arr1[], float Arr2[], float Arr3[] )
{
    for ( int i = 0 ; i < 20 ; i++ )
    {
        Arr3[i] = Arr2[i] - Arr1[i];
    }
}

void displayResults( string Message, float Arr[], int Round )
{
    cout << "The differences in " << Message << " : " << endl << endl << endl;
    
    for ( int i = 0 ; i < 20 ; i++ )
    {
        if ( Arr[i] < 0 )
        {
        //    cout << i << " -> " << " down" << endl;
            cout << fixed << setprecision(2) << -Arr[i];
        }
        else
        {
            if ( Arr[i] > 0 )
            {
                //this is my attempts at the rounding thing with those functions
                cout << i << " -> " << rounding( Arr[i], Round ) << " up" << endl;
            }
            else
            {
                cout << i << " -> stayed the same" << endl;
            }
        }
    }
    
    cout << endl;
}

int main()
{
    float Info2004[20], Info2005[20], Difference[20];
    string Message;
    
    cout << "Enter April 2004 lengths : " << endl;
    getInput( Info2004 );
    
    cout << "Enter April 2005 lengths : " << endl;
    getInput( Info2005 );
    
    getDifference( Info2004, Info2005, Difference );
    Message = "weights";
    displayResults( Message, Difference, 2 );

//*******************

    cout << "Enter April 2004 weights : " << endl;
    getInput( Info2004 );
    
    cout << "Enter April 2005 weights : " << endl;
    getInput( Info2005 );
    
    getDifference( Info2004, Info2005, Difference );
    Message = "lengths";
    displayResults( Message, Difference, 1 );
    
    system( "PAUSE" );
    return 0;
}

Apr 5th, 2005, 10:11 AM	#1
Easter Bunny Programmer Join Date: Mar 2005 Location: different places. constantly on the run. Posts: 57 Rep Power: 4	um, rounding? anyone? g'day, i'm currently studying through correspondence and one of the questions for an assignment has to do with changing pounds to kilo's, or yards to meters or something. that's fine, i can do that, but then it say round up to 2 decimals. i searched the site and quickly googled it, but didn't find anything that made sense. i looked in the books they gave me + the book i got from my mom's library, but that didn't help, because i couldn't find anything. is there something in c++ that lets you set a standard "look" for your numbers like java's DecimalFormat? or do i have to stay up all night and drink lots of (strong) coffee and make my own function thingy that will look at the numbers after the "." and ceil() or floor() or something like that? oh, i'm very new new to c++. started studying this year, so you can't laugh at me and tell all your friends that there's actually a dude who doesn't know how to implement rounding in c++. thanks for the help(in advance of course)and for those who help me, you should pop round sometime and we can have a braai(bbq in english)and talk about integers, strings, etc. it'll be fun.� __________________ There's got to be more to life than being really, really ridiculously good looking

Apr 5th, 2005, 11:20 AM	#2
spydoor Programmer Join Date: Feb 2005 Posts: 64 Rep Power: 4	(Toggle Plain Text) cout << fixed << setprecision(2) << value; cout << fixed << setprecision(2) << value;

Apr 5th, 2005, 5:26 PM	#3
tempest Programming Guru Join Date: Oct 2004 Posts: 1,041 Rep Power: 5	(Toggle Plain Text) float round(float val, int prec) { val = (10^prec); val = (int)val; return val/(float)prec; } float round(float val, int prec) { val = (10^prec); val = (int)val; return val/(float)prec; } __________________ Last edited by tempest; Apr 5th, 2005 at 5:44 PM.

May 3rd, 2005, 10:20 AM	#4
Easter Bunny Programmer Join Date: Mar 2005 Location: different places. constantly on the run. Posts: 57 Rep Power: 4	here you go, this is what i've got. it works on some numbers, but not on all. i end up being out by 0.000000000000...00001 sometimes. sat for hours trying to work something out, but not getting there. the Temp = ceil( f ); part works for the first part of the assignment's test data, but on the second i'm over by 0.000001, then it rounds up and then i'm over by 0.01 or something. stole the recursive function from another post here(thanks dude! ). if i take out the ceil( f ) bit, then on the first bit of data i'm under by 0.01 or so. i'm close to having a hernia. (Toggle Plain Text) int exponent( int Num, int Exp ) { if ( Exp == 0 ) return 1; return ( Num * ( exponent( Num, Exp-1 ) ) ); } float rounding( float f, int Exp ) { int Temp; int Div = exponent( 10, Exp ); f = Div; Temp = ceil( f ); f = (int)Temp; f /= Div; return f; } int exponent( int Num, int Exp ) { if ( Exp == 0 ) return 1; return ( Num ( exponent( Num, Exp-1 ) ) ); } float rounding( float f, int Exp ) { int Temp; int Div = exponent( 10, Exp ); f *= Div; Temp = ceil( f ); f = (int)Temp; f /= Div; return f; } thanks for the help(in advance of course). __________________ There's got to be more to life than being really, really ridiculously good looking

May 3rd, 2005, 10:21 AM	#5
Easter Bunny Programmer Join Date: Mar 2005 Location: different places. constantly on the run. Posts: 57 Rep Power: 4	when i use (Toggle Plain Text) cout << fixed << setprecision(2) << value; cout << fixed << setprecision(2) << value; do i have to include something special, because it doesn't work when i compile. __________________ There's got to be more to life than being really, really ridiculously good looking

May 3rd, 2005, 10:41 AM	#6
BaroN NighT Programmer Join Date: Mar 2005 Location: Lexington, Ky Posts: 58 Rep Power: 4	Yes you do : #include <iomanip> then you can use setprecision(n). n is the number of decimal places you want the program to output.

May 6th, 2005, 7:11 AM	#7
Easter Bunny Programmer Join Date: Mar 2005 Location: different places. constantly on the run. Posts: 57 Rep Power: 4	ok, so i included iomanip, but it still says "'setprecision' undeclared (first use this function)". i'd rather ask a question and look stupid, than be stupid forever, so here goes... (Toggle Plain Text) cout << fixed << setprecision(2) << value; cout << fixed << setprecision(2) << value; what would it look like in my program? this: (Toggle Plain Text) cout << fixed << setprecision(2) << Arr[i]; cout << fixed << setprecision(2) << Arr[i]; Arr[i] is an array of floats. i do feel slightly stupid now, but i'm sure it's not gonna last for long... and think of all the other people you're helping who are too affraid to ask and blah blah blah... thanks. __________________ There's got to be more to life than being really, really ridiculously good looking

May 6th, 2005, 7:56 AM	#8
spydoor Programmer Join Date: Feb 2005 Posts: 64 Rep Power: 4	use namespace std , or fully qualify (Toggle Plain Text) #include <iostream> #include <iomanip> using namespace std; // if you don't do this you have to fully qualify cout, fixed, setprecision ..... int main () { double f =3.14159; cout << fixed << setprecision (2) << f << endl; std::cout << std::fixed << std::setprecision (4) << f << std::endl; return 0; } #include <iostream> #include <iomanip> using namespace std; // if you don't do this you have to fully qualify cout, fixed, setprecision ..... int main () { double f =3.14159; cout << fixed << setprecision (2) << f << endl; std::cout << std::fixed << std::setprecision (4) << f << std::endl; return 0; }

May 6th, 2005, 8:38 AM	#9
Easter Bunny Programmer Join Date: Mar 2005 Location: different places. constantly on the run. Posts: 57 Rep Power: 4	this is the whole thing so far. first two functions i spent hours on, but it doesn't work 100%. (Toggle Plain Text) //assignment 3 --> question 1a #include <iostream> #inclide <iomanip> using namespace std; int exponent( int Num, int Exp ) { if ( Exp == 0 ) return 1; return ( Num * ( exponent( Num, Exp-1 ) ) ); } float rounding( float f, int Exp ) { int Temp; int Div = exponent( 10, Exp ); f = Div; //this worked for the first half of the test data, but second half it's out by a bit // Temp = ceil( f ); f = (int)Temp; f /= Div; return f; } void getInput( float Arr[] ) { for ( int i = 0 ; i < 20 ; i++ ) { cin >> Arr[i]; } } void getDifference( float Arr1[], float Arr2[], float Arr3[] ) { for ( int i = 0 ; i < 20 ; i++ ) { Arr3[i] = Arr2[i] - Arr1[i]; } } void displayResults( string Message, float Arr[], int Round ) { cout << "The differences in " << Message << " : " << endl << endl << endl; for ( int i = 0 ; i < 20 ; i++ ) { if ( Arr[i] < 0 ) { // cout << i << " -> " << " down" << endl; cout << fixed << setprecision(2) << -Arr[i]; } else { if ( Arr[i] > 0 ) { //this is my attempts at the rounding thing with those functions cout << i << " -> " << rounding( Arr[i], Round ) << " up" << endl; } else { cout << i << " -> stayed the same" << endl; } } } cout << endl; } int main() { float Info2004[20], Info2005[20], Difference[20]; string Message; cout << "Enter April 2004 lengths : " << endl; getInput( Info2004 ); cout << "Enter April 2005 lengths : " << endl; getInput( Info2005 ); getDifference( Info2004, Info2005, Difference ); Message = "weights"; displayResults( Message, Difference, 2 ); //****************** cout << "Enter April 2004 weights : " << endl; getInput( Info2004 ); cout << "Enter April 2005 weights : " << endl; getInput( Info2005 ); getDifference( Info2004, Info2005, Difference ); Message = "lengths"; displayResults( Message, Difference, 1 ); system( "PAUSE" ); return 0; } //assignment 3 --> question 1a #include <iostream> #inclide <iomanip> using namespace std; int exponent( int Num, int Exp ) { if ( Exp == 0 ) return 1; return ( Num * ( exponent( Num, Exp-1 ) ) ); } float rounding( float f, int Exp ) { int Temp; int Div = exponent( 10, Exp ); f = Div; //this worked for the first half of the test data, but second half it's out by a bit // Temp = ceil( f ); f = (int)Temp; f /= Div; return f; } void getInput( float Arr[] ) { for ( int i = 0 ; i < 20 ; i++ ) { cin >> Arr[i]; } } void getDifference( float Arr1[], float Arr2[], float Arr3[] ) { for ( int i = 0 ; i < 20 ; i++ ) { Arr3[i] = Arr2[i] - Arr1[i]; } } void displayResults( string Message, float Arr[], int Round ) { cout << "The differences in " << Message << " : " << endl << endl << endl; for ( int i = 0 ; i < 20 ; i++ ) { if ( Arr[i] < 0 ) { // cout << i << " -> " << " down" << endl; cout << fixed << setprecision(2) << -Arr[i]; } else { if ( Arr[i] > 0 ) { //this is my attempts at the rounding thing with those functions cout << i << " -> " << rounding( Arr[i], Round ) << " up" << endl; } else { cout << i << " -> stayed the same" << endl; } } } cout << endl; } int main() { float Info2004[20], Info2005[20], Difference[20]; string Message; cout << "Enter April 2004 lengths : " << endl; getInput( Info2004 ); cout << "Enter April 2005 lengths : " << endl; getInput( Info2005 ); getDifference( Info2004, Info2005, Difference ); Message = "weights"; displayResults( Message, Difference, 2 ); //****************** cout << "Enter April 2004 weights : " << endl; getInput( Info2004 ); cout << "Enter April 2005 weights : " << endl; getInput( Info2005 ); getDifference( Info2004, Info2005, Difference ); Message = "lengths"; displayResults( Message, Difference, 1 ); system( "PAUSE" ); return 0; } __________________ There's got to be more to life than being really, really ridiculously good looking

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Programming Forums > Application Development > C++

um, rounding? anyone?