double.ToString("G_") doesn't work with large numbers

TinyCLR OS
1

I’m having an issue where ToString with format code “G” for doubles or floats does not limit the number of digits for very large numbers, above say 10^19. It worked for small numbers down to 10^-300.

3.1416
31.416
314.16
3141.6
31416
3.1416E+05
3.1416E+06
3.1416E+07
3.1416E+08
3.1416E+09
3.1416E+10
3.1416E+11
3.1416E+12
3.1416E+13
3.1416E+14
3.1416E+15
3.1416E+16
3.1416E+17
3.1416E+18
3.14159265358979312E+19
3.14159265358979312E+20
...
2

I never heard anything about the problem above. Now I have noticed on a related note that ‘double.ToString(“G_”)’ also displays incorrect values for the significand above ~10^62. The value of x remains correct, but the string representation is wrong.

This code produces the output below it:

    static void Main()
    {
        double x = 1;
        string s;
        while(x < double.MaxValue)
        {
            s = x.ToString("G4");
            Debug.WriteLine(s);
            x *= 10;
        }
    }

…1.0E+60
1.0E+61
1.0E+62
1.66E+63
1.66E+64
1.66E+65…

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