conversion from double to char or string

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C++

How do i convert a double to 2 decimal places and display the output as string or char.

Thanks.

Posted 15-Oct-10 6:57am

slimtugo

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4 solutions

Solution 4

If displaying it to the console is the only desire, then just:
printf("%.2f\n", doubleVal);

If you want divide it into two part, just use modf function.

They are indeed two different tasks.

Posted 16-Oct-10 0:29am

Zhan Zongru

Solution 1

use the modf function. This splits your double into the integer part and the fractional part.

Then, take the fractional part and multiply it by a power of 10 in your case, 10^2. Then use the floor function to return just the integer portion of that number and then divide it by the power of 10. Then, add the integer and fractional parts back together.

C

double dblOriginal, dblIntPortion, dblFractPortion;
dblOriginal = 25.4938;

dblFractPortion = modf(dblOriginal, &dblIntPortion);

dblFractPortion = pow(10.0,2) * dblFractPortion;
dblFractPortion = floor(dblFractPortion);
dblFractPortion = dblFractPortion / pow(10.0,2);

cout << (dblIntPortion + dblFractPortion);

This should give you what you're looking for (though I'm a bit rusty on c++).

Posted 15-Oct-10 7:35am

William Winner

Updated 15-Oct-10 8:02am

v2

Solution 3

I would recommend using printf or sprintf

Posted 15-Oct-10 23:07pm

T2102

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Alain Rist · Accepted Answer · 2010-10-15T11:02:00

Using the standard library facilitation is simpler and more versatile:

C++

#include<iomanip>
#include<strstream>
#include<string>

// Converts a double to a string rounded to t_digits decimal positions
template <size_t t_digits>
std::string DoubleToString(double dVal)
{
    std::ostrstream oss;
    oss << std::fixed << std::setprecision(t_digits) << dVal << std::ends;
    return oss.str();
}

Test program:

C++

#include<iostream>
int main()
{
    std::cout << DoubleToString<2>(1234.) << std::endl;
    std::cout << DoubleToString<2>(1.1) << std::endl;
    std::cout << DoubleToString<2>(1234.5678) << std::endl;
    std::cout << DoubleToString<2>(1.2345678) << std::endl;
    std::cout << DoubleToString<4>(1.2345678) << std::endl;
}

cheers,
AR

conversion from double to char or string

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conversion from double to char or string

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