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Merge pull request adafruit#59 from pfalcon/slice
Implement basic slice object and string slicing
2 parents 9ba9589 + f8b9d3c commit b95d90b

9 files changed

Lines changed: 154 additions & 3 deletions

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‎py/mpconfig.h‎

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@@ -25,3 +25,9 @@
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#ifndef MICROPY_MEM_STATS
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#define MICROPY_MEM_STATS (1)
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#endif
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// Whether to support slice object and correspondingly
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// slice subscript operators
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#ifndef MICROPY_ENABLE_SLICE
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#define MICROPY_ENABLE_SLICE (1)
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#endif

‎py/obj.h‎

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@@ -144,6 +144,7 @@ mp_obj_t mp_obj_new_list(uint n, mp_obj_t *items);
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mp_obj_t mp_obj_new_list_reverse(uint n, mp_obj_t *items);
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mp_obj_t mp_obj_new_dict(int n_args);
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mp_obj_t mp_obj_new_set(int n_args, mp_obj_t *items);
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mp_obj_t mp_obj_new_slice(mp_obj_t start, mp_obj_t stop, mp_obj_t step);
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mp_obj_t mp_obj_new_bound_meth(mp_obj_t self, mp_obj_t meth);
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mp_obj_t mp_obj_new_class(struct _mp_map_t *class_locals);
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mp_obj_t mp_obj_new_instance(mp_obj_t clas);
@@ -214,6 +215,10 @@ mp_obj_t mp_obj_dict_store(mp_obj_t self_in, mp_obj_t key, mp_obj_t value);
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// set
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void mp_obj_set_store(mp_obj_t self_in, mp_obj_t item);
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// slice
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extern const mp_obj_type_t slice_type;
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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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// functions
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typedef struct _mp_obj_fun_native_t { // need this so we can define const objects (to go in ROM)
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mp_obj_base_t base;

‎py/objslice.c‎

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@@ -0,0 +1,74 @@
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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

‎py/objstr.c‎

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@@ -27,9 +27,31 @@ mp_obj_t str_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
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const char *lhs_str = qstr_str(lhs->qstr);
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switch (op) {
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case RT_BINARY_OP_SUBSCR:
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// string access
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// XXX a massive hack!
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return mp_obj_new_int(lhs_str[mp_obj_get_int(rhs_in)]);
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// TODO: need predicate to check for int-like type (bools are such for example)
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// ["no", "yes"][1 == 2] is common idiom
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if (MP_OBJ_IS_SMALL_INT(rhs_in)) {
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// TODO: This implements byte string access for single index so far
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// TODO: Handle negative indexes.
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return mp_obj_new_int(lhs_str[mp_obj_get_int(rhs_in)]);
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#if MICROPY_ENABLE_SLICE
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} else if (MP_OBJ_IS_TYPE(rhs_in, &slice_type)) {
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int start, stop, step;
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mp_obj_slice_get(rhs_in, &start, &stop, &step);
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assert(step == 1);
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int len = strlen(lhs_str);
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if (start < 0) {
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start = len + start;
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}
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if (stop <= 0) {
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stop = len + stop;
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}
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return mp_obj_new_str(qstr_from_strn_copy(lhs_str + start, stop - start));
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#endif
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} else {
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// Message doesn't match CPython, but we don't have so much bytes as they
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// to spend them on verbose wording
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nlr_jump(mp_obj_new_exception_msg(rt_q_TypeError, "index must be int"));
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}
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case RT_BINARY_OP_ADD:
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case RT_BINARY_OP_INPLACE_ADD:

‎py/vm.c‎

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@@ -410,6 +410,20 @@ bool mp_execute_byte_code_2(const byte **ip_in_out, mp_obj_t *fastn, mp_obj_t **
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sp++;
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break;
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#if MICROPY_ENABLE_SLICE
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case MP_BC_BUILD_SLICE:
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DECODE_UINT;
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if (unum == 2) {
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obj2 = POP();
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obj1 = TOP();
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SET_TOP(mp_obj_new_slice(obj1, obj2, NULL));
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} else {
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printf("3-argument slice is not supported\n");
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assert(0);
423+
}
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break;
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#endif
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case MP_BC_UNPACK_SEQUENCE:
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DECODE_UINT;
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rt_unpack_sequence(sp[0], unum, sp - unum + 1);

‎stm/Makefile‎

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@@ -78,6 +78,7 @@ PY_O = \
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objnone.o \
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objrange.o \
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objset.o \
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objslice.o \
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objstr.o \
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objtuple.o \
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objtype.o \

‎tests/basics/tests/slice-bstr1.py‎

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@@ -0,0 +1,27 @@
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b"123"[0:1]
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b"123"[0:2]
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b"123"[:1]
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b"123"[1:]
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# Idiom for copying sequence
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b"123"[:]
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b"123"[:-1]
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# Weird cases
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b"123"[0:0]
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b"123"[1:0]
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b"123"[1:1]
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b"123"[-1:-1]
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b"123"[-3:]
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b"123"[-3:3]
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b"123"[0:]
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b"123"[:0]
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b"123"[:-3]
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b"123"[:-4]
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# No IndexError!
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b""[1:1]
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b""[-1:-1]

‎unix-cpy/Makefile‎

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@@ -43,6 +43,7 @@ PY_O = \
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objnone.o \
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objrange.o \
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objset.o \
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objslice.o \
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objstr.o \
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objtuple.o \
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objtype.o \

‎unix/Makefile‎

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@@ -50,6 +50,7 @@ PY_O = \
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objnone.o \
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objrange.o \
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objset.o \
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objslice.o \
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objstr.o \
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objtuple.o \
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objtype.o \

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