int remove_empty_columns(alignment& A) { int length = 0; for(int column=0;column<A.length();column++) if (not all_gaps(A,column)) { if (column != length) for(int i=0;i<A.n_sequences();i++) A.set_value(length,i, A(column,i) ); length++; } int n_empty = A.length() - length; A.changelength(length); return n_empty; }