[FR] Round with precision/decimal place

[thareh]

Good day,

I'd be nice to be able to round floats/doubles to a certain decimal place and also convert floats/doubles to a "nice" looking string.

I've come up with a solution but surely there is a better way, and I don't know if my solution works on other platforms.

#include <sstream>
#include <iomanip>
#include <blitz.h>

extern "C" {
    BBString * bmx_double_to_string(double val, int precision){
        std::ostringstream str;
        str << std::fixed;
        str << std::setprecision(precision);
        str << val;

        return bbStringFromCString(str.str().c_str());
    }
}

Thanks!

[GWRon]

This is my Blitzmax-based solution:

    'convert a double to a string
    'double is rounded to the requested amount of digits after comma
    Function NumberToString:String(number:Double, digitsAfterDecimalPoint:Int = 2, truncateZeros:Int = False)
        Local pow:Int = 10
        For Local i:Int = 1 Until digitsAfterDecimalPoint
            pow :* 10
        Next
        'slower than the loop!
        'local pow:int = int(10 ^ digitsAfterDecimalPoint)

        'bring all decimals in front of the dot, add 0.5 to "round"
        'divide "back" the rounded value
        Local tmp:Double = (number * pow + Sgn(number) * 0.5) / pow

        'find dot - and keep "digitsAfterDecimalPoint" numbers afterwards
        Local dotPos:Int = String(Long(tmp)).length  '+1
        If tmp < 0 Then dotPos :+ 1
        Local s:String = String(tmp)[.. dotPos + 1 + digitsAfterDecimalPoint]
        's = _StrLeft(string(tmp), dotPos + 1 + digitsAfterDecimalPoint)

        'remove 0s? 1.23000 => 1.23, 1.00 = 1
        If truncateZeros
            While s<>"" And _StrRight(s, 1) = "0"
                s = s[.. s.length-1]
            Wend
            'only "xx." left?
            If _StrRight(s, 1) = "." Then s = s[.. s.length-1]
        EndIf
        Return s
    End Function

Yours looks way more concise.

[thareh]

Hey,

Your solution looks very similar to my Blitzmax-based one I used before! 😄