Definion of 'for' statement in the manual
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- Subject: Definion of 'for' statement in the manual
- From: Niccolo Medici <niccolomedici@...>
- Date: 2015年9月24日 19:02:46 +0300
The reference for Lua 5.2 says:
"""
More precisely, a 'for' statement like
for v = e1, e2, e3 do block end
is equivalent to the code:
do
local var, limit, step = tonumber(e1), tonumber(e2), tonumber(e3)
if not (var and limit and step) then error() end
while (step > 0 and var <= limit) or (step <= 0 and var >= limit) do
local v = var
block
var = var + step
end
end
"""
Whereas the reference for Lua 5.3 says it's equivalent to:
"""
do
local var, limit, step = tonumber(e1), tonumber(e2), tonumber(e3)
if not (var and limit and step) then error() end
var = var - step
while true do
var = var + step
if (step >= 0 and var > limit) or (step < 0 and var < limit) then
break
end
local v = var
block
end
end
"""
My question:
Why does Lua 5.3's reference does "var = var - step" instead of simply
moving the "var = var + step" after "block" (as in Lua 5.2)?