import core.math : sqrt;
import std.math.constants : LN10, PI;
import std.math.operations : isClose;

auto a = complex(2.0, 1.0);
assert(log10(a) == log(a) / log(complex(10.0)));

auto b = log10(complex(0.0, 1.0)) * 2.0;
auto c = log10(complex(sqrt(2.0) / 2, sqrt(2.0) / 2)) * 4.0;
assert(isClose(b, c, 0.0, 1e-15));