[NTG-context] lpdf.checkedkey has problem with false values

Peter Rolf indiego at gmx.net
Mon Sep 15 16:59:56 CEST 2014


Am 15.09.2014 um 16:14 schrieb Michail Vidiassov:
> Dear Developers and All,
> 
> lpdf.checkedkey routine from lpdf-ini.lua has problems with accessing
> false boolean values, it returns them as nil. Is it by design or
> neglect?

More a lua design decision. 'nil' is equal to 'false' here, 'true' is
equal to all that is not 'nil'.

http://www.lua.org/pil/3.3.html

> (I vaguely remember stumbling on this problems before, so  there is a
> chance that I have already got the answer, but have forgotten it.)
> The minimal demo:
> \starttext
> \startluacode
> local function writebool(bv,text)
>  if bv == true then

if bv then

>   io.write(text, " true \n")
>  elseif bv == nil then

else
(if not bv then)


HTH,   Peter


>   io.write(text, " nil  \n")
>  else
>   io.write(text, " false\n")
>  end
> end
> local a = {}
> a["x"] = true
> a["y"] = false
> a["z"] = nil
> writebool(lpdf.checkedkey(a,"x","boolean"),"lpdf.checkedkey(a,\"x\",\"boolean\")")
> writebool(lpdf.checkedkey(a,"y","boolean"),"lpdf.checkedkey(a,\"y\",\"boolean\")")
> writebool(lpdf.checkedkey(a,"z","boolean"),"lpdf.checkedkey(a,\"z\",\"boolean\")")
> writebool(a.x,"a.x")
> writebool(a.y,"a.y")
> writebool(a.z,"a.z")
> \stopluacode
> TEST
> \stoptext
> 
> 
> It results in the following relevant output
> 
> lpdf.checkedkey(a,"x","boolean") true
> lpdf.checkedkey(a,"y","boolean") nil
> lpdf.checkedkey(a,"z","boolean") nil
> a.x true
> a.y false
> a.z nil
> 
> Note that false value was read by checkedkey as nil.
> 
> Sincerely, MIchail
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