How to replace the keyword "nan" to check the contract assert?

[Dennis Ritchie via Digitalmars-d-learn]

Hi,
How do I replace double.init?

import std.stdio : writeln;
import std.algorithm : uninitializedFill;
void main() {

        double[] arr = new double[6];
        uninitializedFill(arr[0 .. $ - 2], 3.25);
        writeln(arr);
	assert(arr == [3.25, 3.25, 3.25, 3.25, double.init, 
double.init]); /* not work */
}