Cheap way to add Lua 5.3 partial bit32 compatibility
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- Subject: Cheap way to add Lua 5.3 partial bit32 compatibility
- From: Enrico Colombini <erix@...>
- Date: Wed, 6 May 2015 14:48:01 +0200
I was looking for a simple way to make a Lua 5.2 program work with Lua
5.3 too, so I had to select either bit32 or the new native bitwise
operators, depending on the Lua interpreter used.
My first try was a failure:
-- this will not load on Lua 5.2 because of the '|'
local bor = bit32 and bit32.bor or function(a, b) return a | b end
So I added a new module:
file: bitops52.lua
------------------------------------------------
-- cheap Lua 5.2 basic bitwise operators emulation
-- 2 arguments only (and of course relatively slow)
return {
band = function(a, b) return a & b end,
bor = function(a, b) return a | b end,
bxor = function(a, b) return a ~ b end,
bnot = function(a) return ~a end,
rshift = function(a, n) return a >> n end,
lshift = function(a, n) return a << n end,
}
------------------------------------------------
and loaded it only when needed:
local bit32 = bit32 or require('bitops52')
This way, the Lua 5.3-specific operators in 'bitops52' are never seen by
the Lua 5.2 loader and the program works fine with both Lua versions.
--
Enrico