how to rand a decimal value in range [0-1] by c++,similar with javascript Math.random()

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i have got a html with a javascript Math.random()，the source as follow:

XML

<HTML>
 <HEAD>
  <script language="javascript">
    function changecode1(obj)
    {
        obj.src="http://www.chinawestair.net/jcaptcha?.tmp="+Math.random();;
        alert(obj.src);
    }
  </script>
 </HEAD>

 <BODY>
    <table>
        <tr>
            <td width="200" height="30" align="left">
                validate code:
                <img id="jcaptcha" src="http://www.chinawestair.net/jcaptcha?.tmp=0.06781555591097987" onclick="javascript:changecode1(this)" style="cursor: pointer;height:28px;" title="change pic" border=0 />
            </td>
        </tr>
    </table>

 </BODY>
</HTML>

Now,i have write a c++ program in windows console app trying to simulate the function Math.Random().

The return value must in range [0-1] with zero in the first word,next is point,last is length of 16 number,for example "0.06781555591097987"

i need your help, give me some better advice plz.

thanks a lot.

Posted 30-May-11 0:30am

ariesj2w

Updated 30-May-11 0:34am

v2

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వేంకటనారాయణ(venkatmakam) · Answer 1 · 2011-05-30T00:58:00

I did not get the last point if you wand 16 precision(16 number after '.') use the following code,

MIDL

srand( (unsigned)time( NULL ) );
double d = (rand()/(double)RAND_MAX);
printf("%0.16lf",d);

if you want 16 digits after 0.0 use this code,

MIDL

srand( (unsigned)time( NULL ) );
double d = (rand()/(double)RAND_MAX);
printf("%0.17lf",0.1*d);

ariesj2w · Answer 2 · 2011-05-30T16:15:00

Solution 3

i think the following sentence should be make some compatibility problem...
printf("%0.17lf",0.1*d);

when i use c++,it works,but it isn't works in g++...
printf("0.16f", d);

this should be perfect i think

thank you for venkatmakam&Timberbird's warmly help.

=。=

Posted 30-May-11 16:15pm

ariesj2w

Timberbird · Answer 3 · 2011-05-30T00:44:00

Solution 1

Why not use rand() function?

Posted 30-May-11 0:44am

Timberbird