diff options
| -rw-r--r-- | py/objslice.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/py/objslice.c b/py/objslice.c index 619899b232..03607e4c3e 100644 --- a/py/objslice.c +++ b/py/objslice.c @@ -39,8 +39,23 @@ const mp_obj_type_t slice_type = { // TODO: Make sure to handle "empty" values, which are signified by None in CPython mp_obj_t mp_obj_new_slice(mp_obj_t ostart, mp_obj_t ostop, mp_obj_t ostep) { assert(ostep == NULL); - machine_int_t start = mp_obj_get_int(ostart); - machine_int_t stop = mp_obj_get_int(ostop); + machine_int_t start = 0, stop = 0; + if (ostart != mp_const_none) { + start = mp_obj_get_int(ostart); + } + if (ostop != mp_const_none) { + stop = mp_obj_get_int(ostop); + if (stop == 0) { + // [x:0] is a special case - in our slice object, stop = 0 means + // "end of sequence". Fortunately, [x:0] is an empty seqence for + // any x (including negative). [x:x] is also always empty sequence. + // but x also can be 0. But note that b""[x:x] is b"" for any x (i.e. + // no IndexError, at least in Python 3.3.3). So, we just use -1's to + // signify that. -1 is catchy "special" number in case someone will + // try to print [x:0] slice ever. + start = stop = -1; + } + } mp_obj_slice_t *o = m_new(mp_obj_slice_t, 1); o->base.type = &slice_type; o->start = start; |