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<dpl@sun.ac.za<mailto:dpl@sun.ac.za>> 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 code. Dirk
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( io.open( 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!" fh:close() ---------------------------------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