MQL4 StringToDouble / StrToDouble alters the value of the variable?

[Millard Melnyk]

MQL4 documentation states that the value limits for double type variables is:

"Minimal Positive Value" = 2.2250738585072014e-308

"Maximum Value" = 1.7976931348623158e+308. 

(See https://docs.mql4.com/basis/types/double)

So why does StringToDouble alter the value converted?

Or am I doing one thing unawares here while expecting a different result?

void OnStart()
{
string s1 = "5554535251504900090807060504030201";
double d1 = StringToDouble(s1);
string s2 = DoubleToString(d1);

Print("s2<",s2,">");
printf("d1<%035.8f>",d1);
Print("s1<",s1,">");
     
return;
}

Here's what I get when I run that code:

s1<5554535251504900090807060504030201>

d1<5554535251504899684469244159852544.00000000>

s2<5554535251504899684469244159852544>

---

5554535251504900090807060504030201 amounts to 5.55454E+33.

Obviously, that doesn't even come remotely close to the 1.7976931348623158e+308 limit. 

What is changing the value of the variable? What am I missing here?

[William Roeder]

Doubles only have 15 digits of accuracy.
          Double-precision floating-point format - Wikipedia, the free encyclopedia