besselJ

1 assert(std.math.approxEqual(besselJ(2, 1),
2 	0.5767248077568733872024482422691));
3 assert(std.math.approxEqual(besselJ(20, 1),
4 	0.066833124175850045578992974193));
5 assert(std.math.approxEqual(besselJ(1, 1.2), 0.351884));