truncate

static VALUE
flo_truncate(VALUE num)
{
    double f = RFLOAT_VALUE(num);
    long val;

    if (f > 0.0) f = floor(f);
    if (f < 0.0) f = ceil(f);

    if (!FIXABLE(f)) {
        return rb_dbl2big(f);
    }
    val = (long)f;
    return LONG2FIX(val);
}