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On 05/02/15 10:00 PM, Sean Conner wrote:

It was thus said that the Great Soni L. once stated:

  It's (in my opinion) cleaner and easier to read.  Now my question:  can
I rely upon this behavior of io.lines() and string.gmatch() to only
return a single function?  I tested it on Lua 5.1, 5.2, 5.3 and LuaJIT,
and in each case, only a function was returned.  Am I relying upon an
implementation detail?  Should I use the first version, where I pass in
the state and value each time, to be "safe"?


According to the manual:
http://www.lua.org/manual/5.3/manual.html#pdf-string.gmatch

"Returns an *iterator function*"

I believe it is safe to assume "iterator function" means it returns only
a function that returns the next match or nil at the end. (If it said
just "an iterator", THEN it wouldn't be safe to assume so)

   I think Roberto will have to chime in here because of replies from
Daurnimator:


Yes. this is an implementation detail. please do not rely on it.  It just
happens to be that state and 'var_1' are nil
IIRC this caught out a few people/modules when run under alternate 
implementations (was it Kahlua?)

Sounds like a non-compliant implementation to me.

and Roberto:


I guess the best solution is not to use lines/gmatch at all, but
read/match (or find).  See [1] for something similar.

[1] http://www.lua.org/pil/7.1.html
This says nothing about the reference manual, tho. (or am I missing something?) 
   Either it's documented that io.lines() (and a few others) only return a
function, or the manual may need some clarification.

   -spc




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