Re: Multiple assignment, numeric table keys
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- Subject: Re: Multiple assignment, numeric table keys
- From: Luiz Henrique de Figueiredo <lhf@...>
- Date: 2012年12月12日 09:39:00 -0200
> Can someone just confirm my thoughts that the first example is always wrong, and the second will always work.
Look at the bytecode below. You'll see that #t is computed (twice, but
from the same table) before any assignment takes place. This is what
happens in general in multiple assignments: all receiving locations are
found before the values.
% luac -l -p -
t[#t+1], t[#t+1] = 1, 2
^D
main <stdin:0,0> (12 instructions at 0x104701650)
0+ params, 5 slots, 1 upvalue, 0 locals, 3 constants, 0 functions
1 [1] GETTABUP 0 0 -1 ; _ENV "t"
2 [1] GETTABUP 1 0 -1 ; _ENV "t"
3 [1] LEN 1 1
4 [1] ADD 1 1 -2 ; - 1
5 [1] GETTABUP 2 0 -1 ; _ENV "t"
6 [1] GETTABUP 3 0 -1 ; _ENV "t"
7 [1] LEN 3 3
8 [1] ADD 3 3 -2 ; - 1
9 [1] LOADK 4 -2 ; 1
10 [1] SETTABLE 2 3 -3 ; - 2
11 [1] SETTABLE 0 1 4
12 [1] RETURN 0 1