John R. Lenton
11 years ago
11 changed files with 168 additions and 11 deletions
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#include <stdlib.h> |
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#include <stdint.h> |
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#include <string.h> |
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#include <assert.h> |
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#include "nlr.h" |
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#include "misc.h" |
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#include "mpconfig.h" |
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#include "obj.h" |
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#include "runtime0.h" |
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#if MICROPY_ENABLE_SLICE |
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// TODO: This implements only variant of slice with 2 integer args only.
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// CPython supports 3rd arg (step), plus args can be arbitrary Python objects.
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typedef struct _mp_obj_slice_t { |
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mp_obj_base_t base; |
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machine_int_t start; |
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machine_int_t stop; |
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} mp_obj_slice_t; |
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void slice_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t o_in) { |
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mp_obj_slice_t *o = o_in; |
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print(env, "slice(" INT_FMT ", " INT_FMT ")", o->start, o->stop); |
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} |
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const mp_obj_type_t slice_type = { |
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{ &mp_const_type }, |
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"slice", |
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slice_print, |
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NULL, // call_n
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NULL, // unary_op
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NULL, // binary_op
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NULL, // getiter
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NULL, // iternext
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{ { NULL, NULL }, }, // method list
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}; |
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// TODO: Make sure to handle "empty" values, which are signified by None in CPython
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mp_obj_t mp_obj_new_slice(mp_obj_t ostart, mp_obj_t ostop, mp_obj_t ostep) { |
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assert(ostep == NULL); |
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machine_int_t start = 0, stop = 0; |
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if (ostart != mp_const_none) { |
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start = mp_obj_get_int(ostart); |
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} |
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if (ostop != mp_const_none) { |
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stop = mp_obj_get_int(ostop); |
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if (stop == 0) { |
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// [x:0] is a special case - in our slice object, stop = 0 means
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// "end of sequence". Fortunately, [x:0] is an empty seqence for
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// any x (including negative). [x:x] is also always empty sequence.
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// but x also can be 0. But note that b""[x:x] is b"" for any x (i.e.
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// no IndexError, at least in Python 3.3.3). So, we just use -1's to
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// signify that. -1 is catchy "special" number in case someone will
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// try to print [x:0] slice ever.
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start = stop = -1; |
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} |
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} |
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mp_obj_slice_t *o = m_new(mp_obj_slice_t, 1); |
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o->base.type = &slice_type; |
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o->start = start; |
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o->stop = stop; |
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return (mp_obj_t)o; |
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} |
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void mp_obj_slice_get(mp_obj_t self_in, machine_int_t *start, machine_int_t *stop, machine_int_t *step) { |
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assert(MP_OBJ_IS_TYPE(self_in, &slice_type)); |
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mp_obj_slice_t *self = self_in; |
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*start = self->start; |
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*stop = self->stop; |
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*step = 1; |
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} |
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#endif |
@ -0,0 +1,27 @@ |
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print(b"123"[0:1]) |
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print(b"123"[0:2]) |
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print(b"123"[:1]) |
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print(b"123"[1:]) |
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# Idiom for copying sequence |
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print(b"123"[:]) |
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print(b"123"[:-1]) |
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# Weird cases |
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print(b"123"[0:0]) |
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print(b"123"[1:0]) |
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print(b"123"[1:1]) |
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print(b"123"[-1:-1]) |
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print(b"123"[-3:]) |
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print(b"123"[-3:3]) |
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print(b"123"[0:]) |
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print(b"123"[:0]) |
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print(b"123"[:-3]) |
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print(b"123"[:-4]) |
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# No IndexError! |
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print(b""[1:1]) |
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print(b""[-1:-1]) |
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