New submission from Serhiy Storchaka:
For now complex code is generated for chained comparing.
$ echo "x = a < b > c < d" | ./python -m dis
1 0 LOAD_NAME 0 (a)
2 LOAD_NAME 1 (b)
4 DUP_TOP
6 ROT_THREE
8 COMPARE_OP 0 (<)
10 JUMP_IF_FALSE_OR_POP 28
12 LOAD_NAME 2 (c)
14 DUP_TOP
16 ROT_THREE
18 COMPARE_OP 4 (>)
20 JUMP_IF_FALSE_OR_POP 28
22 LOAD_NAME 3 (d)
24 COMPARE_OP 0 (<)
26 JUMP_FORWARD 4 (to 32)
>> 28 ROT_TWO
30 POP_TOP
>> 32 STORE_NAME 4 (x)
34 LOAD_CONST 0 (None)
36 RETURN_VALUE
Proposed patch adds CHAINED_COMPARE_OP opcode that does all necessary stack
manipulatios. Using it the generated code is simpler:
$ echo "x = a < b > c < d" | ./python -m dis
1 0 LOAD_NAME 0 (a)
2 LOAD_NAME 1 (b)
4 CHAINED_COMPARE_OP 0 (<)
6 JUMP_IF_FALSE_OR_POP 18
8 LOAD_NAME 2 (c)
10 CHAINED_COMPARE_OP 4 (>)
12 JUMP_IF_FALSE_OR_POP 18
14 LOAD_NAME 3 (d)
16 COMPARE_OP 0 (<)
>> 18 STORE_NAME 4 (x)
20 LOAD_CONST 0 (None)
22 RETURN_VALUE
----------
components: Interpreter Core
files: chained_compare_op.patch
keywords: patch
messages: 267466
nosy: Demur Rumed, Mark.Shannon, serhiy.storchaka
priority: normal
severity: normal
stage: patch review
status: open
title: Add CHAINED_COMPARE_OP opcode
type: enhancement
versions: Python 3.6
Added file: http://bugs.python.org/file43247/chained_compare_op.patch
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<http://bugs.python.org/issue27236>
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