/*
 * call-seq:
 *   row.each { |column, value| block } -> row
 *   row.each { |value| block } -> row
 *
 * Iterate with values or column,value pairs.
 */
static VALUE
pgrow_each(self)
    VALUE self;
{
    int arity = NUM2INT(rb_funcall(rb_block_proc(), rb_intern("arity"), 0));
    if (arity == 2) {
        pgrow_each_pair(self);
    }
    else {
        pgrow_each_value(self);
    }
    return self;
}