[luatex] Using libraries from luarocks

[ARATA Mizuki]

Hi Nils,

The value returned by :entry("DateTime") is a userdata, not a string.
Although (the standard) print() automatically converts it to a string via tostring(), tex.print() does not.
Therefore, you need to call tostring() manually, like this:
> tex.print(tostring(data:ifd("0"):entry("DateTime")))

-- 
ARATA Mizuki


> H30/10/13 5:33、Nils Pickert <nils at mipi.de>のメール:
> 
> Sorry, copied the wrong error message: it actually says "no string to
> print"...
> 
> Am 12.10.18 um 22:19 schrieb Nils Pickert:
>> Hi
>> 
>> I got a bit further... Now everything runs fine in Lua directly:
>> Lua 5.3.5  Copyright (C) 1994-2018 Lua.org, PUC-Rio
>>> exif = require ("exif")
>>> data = exif.loadfile("DSCF0274.jpg")
>>> print(data:ifd("0"):entry("DateTime"))
>> 2018:10:12 19:59:32
>>> print(data:ifd("0"):entry("Make"))
>> FUJIFILM
>> 
>> But if I run the same from LuaLaTeX with
>> \directlua{
>> exif = require("exif")
>> data = exif.loadfile("DSCF0274.jpg")
>> tex.print(data:ifd("0"):entry("DateTime"))
>> }
>> 
>> 
>> I get "attempt to index a nil value (global 'data')"
>> which seems to point at that data is not filled at all, and
>> exif.loadfile does nothing...
>> 
>> Any pointers on where to look?
>> 
>> Thanks and best regards
>> Nils
>> 
>> 
>> 
>> Am 08.10.18 um 18:49 schrieb Nils Pickert:
>>> Thanks a lot! It seems to work, now I get the same error message as I
>>> get in naked Lua :-)
>>> 
>>> (relinked my symbolic link lualatex to point to luatex53, hoping that it
>>> does not mess around with the other stuff I am playing with)
>>> 
>>> Thanks again!
>>> Nils
>>> 
>>> 
>>> Am 08.10.18 um 14:52 schrieb luigi scarso:
>>>> 
>>>> 
>>>> On Mon, Oct 8, 2018 at 2:49 PM Martin Wilhelm Leidig
>>>> <listwatch at moss.in-berlin.de <mailto:listwatch at moss.in-berlin.de>> wrote:
>>>> 
>>>>    Am 2018-10-08 um 14.05 schrieb luigi scarso <luigi.scarso at gmail.com
>>>>    <mailto:luigi.scarso at gmail.com>>:
>>>>> 
>>>>> luatex vs luatex53
>>>> 
>>>>    Fascinating.  Thanks for the hint!
>>>> 
>>>> 
>>>> Very likely next texlive will have 
>>>> "luatex"  with lua 5.3 , and perhaps "luatex54" with lua 5.4
>>>> 
>>>> -- 
>>>> luigi
>>> 
>> 
>