RE: code generation bug
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- Subject: RE: code generation bug
- From: "Kelley, Brian" <bkelley@...>
- Date: 2009年4月16日 16:25:47 -0700
Linker: Your third case "1 or false and true or false" is not a bug. Due to operator precedence it is equivalent to "1 or (false and true) or false".
I can generalize the problem a bit, though. For any X, Y, Z, where X ~=nil and X~=false:
((X or Y) and true) or Z --> X (should always be true)
(X or Y) and (true or Z) --> X (should always be true)
Extra parentheses are for clarity and do not affect the results.
-bhk
________________________________________
From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of Linker
Sent: Wednesday, April 15, 2009 11:47 PM
To: Lua list
Subject: Re: code generation bug
I had try it in Lua 5.1.4 win xp:
> =1 or false
1 -- right
> =1 and true or false
true -- right
> =1 or false and true or false
1 -- wrong
> =((1 or false) and true)or false
1 -- wrong
>
On Thu, Apr 16, 2009 at 12:37, Kelley, Brian <bkelley@qualcomm.com> wrote:
I was surprised to notice the following:
Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio
> =((1 or false) and true) or false
1
Same results on 5.1.2 and 5.1.3, MacOS and Windows.
For what it's worth, I observed in lcode.c that the OPR_AND expression inherited the 'k' (kind) of VTRUE from its rhs subexpression, which seems wrong and seems to throw off the subsequent call to luaK_goiffalse().
-bhk
--
Regards,
Linker Lin
linker.m.lin@gmail.com