static int get_column_id(int num)
{
	assert(num >= 0);
	assert((size_t) num < ncolumns);
	assert((size_t) columns[num] < ARRAY_SIZE(infos));
	return columns[num];
}
static int get_column_id(int num)
{
	assert(num >= 0);
	assert((size_t) num < ncolumns);
	assert((size_t) columns[num] < ARRAY_SIZE(infos));
	return columns[num];
}