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On 04/08/2011 11.18, Dirk Laurie wrote:
On Thu, Aug 04, 2011 at 10:32:51AM +0200, liam mail wrote:

On 4 August 2011 07:43, Dirk Laurie<<>>  wrote:
The real story is: "Lua has no integer type, as it does not need it.
… a Lua number can represent any long integer without rounding problems."
(PiL, §2.3).  Sounds good to me.

I think you are looking at the first edition, in the second edition this
was corrected.

Yes, I copied-and-pasted from a window.  The second edition says "32-bit
integer".  The rest of my post makes clear that I was talking about that.

Added to that Lua 5.2 does in fact have an int type.

Please elaborate, giving a cut-and-paste of an interactive session and/or
a quote from the reference manual and/or an excerpt from the beta source


There are times where 4Gb are a real limit:

-- test to see if Lua can seek on a very huge file (>4Gb)
local fname = [[c:\lua-seek-test.dat]]

local fh = assert( fname, 'w+b' ) )
local n = 2^32 + 4
local pos = assert( fh:seek( 'set', n ) )
print( "New position at " .. pos .. " bytes from the beginning of the file." )
fh:write "hello!"

On my system with 5.1.4 and 5.2 this creates a file of 4 bytes instead of more than 4Gb.

Moreover, if you make n = 2^31 + 4, you get a nasty error, because seek wraps it internally to a negative integer!

On todays' systems a 4Gb file is not too uncommon (a DVD ISO image anyone?). Lua should be able to cope with those, IMO.

So, as I stated in another branch of this thread, this is a real problem and programmers should have better info from the reference on the subject.

And the problem could be worse on machines with smaller int widths (embedded systems?) - could 2^16 + 4 be wrapped on those machines?.

-- Lorenzo