build-slice operator

[obriencj]

similar to the builders for tuple and list, provide a builder for slices.

[obriencj]

sibilant > (define FOO (list (range 0 100)))
sibilant > (disassemble-expr (setf (item-slice FOO 25 76) (item-slice FOO start: 75 stop: 24 step: -1)))
  1           0 LOAD_GLOBAL              0 (FOO)
              2 LOAD_CONST               1 (75)
              4 LOAD_CONST               2 (24)
              6 LOAD_CONST               3 (-1)
              8 BUILD_SLICE              3
             10 BINARY_SUBSCR
             12 LOAD_GLOBAL              0 (FOO)
             14 LOAD_CONST               4 (25)
             16 LOAD_CONST               5 (76)
             18 BUILD_SLICE              2
             20 STORE_SUBSCR
             22 LOAD_CONST               0 (None)
             24 RETURN_VALUE
sibilant > (setf (item-slice FOO 25 76) (item-slice FOO start: 75 stop: 24 step: -1))
sibilant > FOO
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]
sibilant > 

[obriencj]

>>> FOO = list(range(0, 100))
>>> def example():
...     FOO[25:76] = FOO[75:24:-1]
...     return FOO
... 
>>> import dis
>>> dis.dis(example)
  2           0 LOAD_GLOBAL              0 (FOO)
              2 LOAD_CONST               1 (75)
              4 LOAD_CONST               2 (24)
              6 LOAD_CONST               6 (-1)
              8 BUILD_SLICE              3
             10 BINARY_SUBSCR
             12 LOAD_GLOBAL              0 (FOO)
             14 LOAD_CONST               4 (25)
             16 LOAD_CONST               5 (76)
             18 BUILD_SLICE              2
             20 STORE_SUBSCR

  3          22 LOAD_GLOBAL              0 (FOO)
             24 RETURN_VALUE
>>> FOO
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]
>>>