Can this code be simplified in one if test instead two?
nil
and ''
are different values. If you need to test that s
is neither, IMO you should just compare against both, because it makes your intent the most clear.
That and a few alternatives, with their generated bytecode:
if not foo or foo == '' then end
GETGLOBAL 0 -1 ; foo
TEST 0 0 0
JMP 3 ; to 7
GETGLOBAL 0 -1 ; foo
EQ 0 0 -2 ; - ""
JMP 0 ; to 7
if foo == nil or foo == '' then end
GETGLOBAL 0 -1 ; foo
EQ 1 0 -2 ; - nil
JMP 3 ; to 7
GETGLOBAL 0 -1 ; foo
EQ 0 0 -3 ; - ""
JMP 0 ; to 7
if (foo or '') == '' then end
GETGLOBAL 0 -1 ; foo
TEST 0 0 1
JMP 1 ; to 5
LOADK 0 -2 ; ""
EQ 0 0 -2 ; - ""
JMP 0 ; to 7
The second is fastest in Lua 5.1 and 5.2 (on my machine anyway), but difference is tiny. I'd go with the first for clarity's sake.