Approximate Pi using randomly scattered points

pi.d

auto approximate(double radius, uint npoints)
{
	import std.range : generate, take;
	import std.algorithm : count;
	import std.random : Xorshift, unpredictableSeed, uniform;

	auto radius2 = radius * radius;
	auto generator = Xorshift(unpredictableSeed);
	auto makeRandomCoord() { return uniform!`[]`(0, radius, generator) ^^ 2; }
	
	return generate(() => makeRandomCoord() + makeRandomCoord())
		.take(npoints)
		.count!(r => r <= radius2)
		* 4.0 / npoints;
}

void main()
{
	import std.range : iota;
	import std.algorithm : map;
	import std.stdio : writefln;
	import std.math : abs;

	enum pi = 3.14159265359;
	foreach (radius; iota(0, 10).map!(n => 10 ^^ n)) {
		writefln("%(%15s%)",
			iota(0, 8).map!(m => abs(approximate(radius, 10 ^^ m) - pi)));
	}
}