http://www.newton-inc.com/dev/techinfo/qa/qa.htmSqrt with a negative number on the Newton, or use Compile in the NTK Inspector, I get a strange result. However, if I just type sqrt(-2) into the listener I get a different strange result. What's going on? call compile("sqrt(-2)") with ()
#4412F2D -1.79769e+308
sqrt(-2)
#440DE05 1.00000e+999
Sqrt on the Newton OS. When passed a negative number, the large positive value is returned instead of a not-a-number value. You can work around it using Pow(x, 0.5) instead of Sqrt(x) if there is no way to guarantee that the value passed to Sqrt is non-negative, or simply check and see if the argument is less than 0 and return a not-a-number constant.sqrt(-2) works differently when you type it into the NTK Inspector is because of a compiler process known as constant folding. Sqrt can be evaluated at compile time if you pass it a constant argument. So what's really happening is that NTK is evaluating the Sqrt function during the compile phase and passing the resulting floating point number (or rather, not-a-number) to the Newton device where it's promptly returned. An NTK real number formatting limitation displays non-a-number values and infinities as 1.00000e+999 rather than as some other string. You can use IsNAN to determine if a real number is a not-a-number value. x := -2;
y := sqrt(x);
#C4335B1 -1.79769e+308
FormattedNumberStr does not properly handle not-a-number values. (it returns "Number too small.")