typeid: to get type of object
writeln("typeid(genotype_matrix): ", typeid(genotype_matrix)); // GenotypeCombinator[][]
writeln("typeid(symbols): ", typeid(symbols)); // ObservedGenotypes
A GenotypeCombinator is a list of TrueGenotypes?
auto a = new bool[n_wanted];
a[] = false;
auto b = new bool[n][m];
b[][] = false;