Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
On Tue, Oct 15, 2019 at 10:15:34AM +0200, Hans Hagen wrote:
> On 10/15/2019 10:04 AM, Taco Hoekwater wrote:
> > Hi Rudolf,
> >
> > > On 15 Oct 2019, at 00:50, Rudolf Bahr wrote:
> > >
> > > Now to your suggestion not to use "assert ()". Indeed it's a solution! My
> > > program
> > > works! I append again its output (again just for fun!). Did you really
> > > try it or
> > > has it been just an idea?
> >
> > First, let me say that embedded lua versions are typically a little bit
> > different
> > from standalone. Just how much different depends on the embedding program.
> > Luatex
> > is actually pretty close to standalone lua. Luatex adds a bunch of
> > extension libraries,
> > but it changes very little of the core language. And all those changes are
> > documented
> > in the luatex manual. None of those changes affect your minimal example,
> > except
> > that lua errors are handled a little differently.
> >
> > Note that standalone lua *also* produces an error, as that is what assert()
> > is
> > supposed to do. And when lua runs into an error, it ignores the rest of the
> > current
> > chunk:
> >
> >“... whenever an error occurs, Lua ends the current chunk and returns
> >to the application.” (from lua.org)
> >
> > Standalone lua typically sees only one chunk (the file you pass on the
> > command
> > line) but embedded lua implementation often see (sometimes many) more
> > chunks.
> > In luatex’s case, each \directlua is a separate chunk (in ConTeXt, that
> > means every
> > \startluacode block and every \ctxlua call is a separate chunk).
> >
> > The only unusual thing here is that standalone lua silently quits and
> > returns a
> > non-zero exit code to the shell, whereas luatex gives you the typical
> > TeX-style
> > error prompt. The rationale for that is: lua errors can happen in many
> > places in
> > your input file, and if they were silently ignored, your typeset pages
> > could be
> > wrong without you realising it.
> >
> >
> > And to answer your question above: I did not have to try or guess. I know
> > about
> > how assert() works because it is documented in the lua manual (and as it
> > closely
> > mimics the assert() C function, that is easy for me to remember).
> as you say, it's all normal lua behaviour:
>
> if you do:
>
> print(io.open("crap.crap"))
>
> one gets
>
> nil crap.crap: No such file or directory2
>
> and i think that assert then returns the second returned argument
>
> but if one does
>
> context(io.open("crap.crap") and "yes" or "no")
>
> then the first argument is checked against
>
> Hans
Hi Hans, hi Taco!
For your answers and patient explanations I want to thank you, not to forget
[1], [2], [3] for instance! Now it gets clearer to me what the distinctive
features could be which one can encounter when using a combination of even so
wunderful programming languages as ConTeXt and Lua are!
Best wishes,
Rudolf
[1] https://wiki.contextgarden.net/Programming_in_LuaTeX
[2] http://www.luatex.org/svn/trunk/manual/luatex.pdf
[3] http://www.pragma-ade.com/general/manuals/cld-mkiv.pdf
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Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
On 10/15/2019 10:04 AM, Taco Hoekwater wrote:
Hi Rudolf,
On 15 Oct 2019, at 00:50, Rudolf Bahr wrote:
Now to your suggestion not to use "assert ()". Indeed it's a solution! My
program
works! I append again its output (again just for fun!). Did you really try it or
has it been just an idea?
First, let me say that embedded lua versions are typically a little bit
different
from standalone. Just how much different depends on the embedding program.
Luatex
is actually pretty close to standalone lua. Luatex adds a bunch of extension
libraries,
but it changes very little of the core language. And all those changes are
documented
in the luatex manual. None of those changes affect your minimal example, except
that lua errors are handled a little differently.
Note that standalone lua *also* produces an error, as that is what assert() is
supposed to do. And when lua runs into an error, it ignores the rest of the
current
chunk:
“... whenever an error occurs, Lua ends the current chunk and returns
to the application.” (from lua.org)
Standalone lua typically sees only one chunk (the file you pass on the command
line) but embedded lua implementation often see (sometimes many) more chunks.
In luatex’s case, each \directlua is a separate chunk (in ConTeXt, that means
every
\startluacode block and every \ctxlua call is a separate chunk).
The only unusual thing here is that standalone lua silently quits and returns a
non-zero exit code to the shell, whereas luatex gives you the typical TeX-style
error prompt. The rationale for that is: lua errors can happen in many places in
your input file, and if they were silently ignored, your typeset pages could be
wrong without you realising it.
And to answer your question above: I did not have to try or guess. I know about
how assert() works because it is documented in the lua manual (and as it closely
mimics the assert() C function, that is easy for me to remember).
as you say, it's all normal lua behaviour:
if you do:
print(io.open("crap.crap"))
one gets
nil crap.crap: No such file or directory2
and i think that assert then returns the second returned argument
but if one does
context(io.open("crap.crap") and "yes" or "no")
then the first argument is checked against
Hans
-
Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-
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Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
Hi Rudolf, > On 15 Oct 2019, at 00:50, Rudolf Bahr wrote: > > Now to your suggestion not to use "assert ()". Indeed it's a solution! My > program > works! I append again its output (again just for fun!). Did you really try it > or > has it been just an idea? First, let me say that embedded lua versions are typically a little bit different from standalone. Just how much different depends on the embedding program. Luatex is actually pretty close to standalone lua. Luatex adds a bunch of extension libraries, but it changes very little of the core language. And all those changes are documented in the luatex manual. None of those changes affect your minimal example, except that lua errors are handled a little differently. Note that standalone lua *also* produces an error, as that is what assert() is supposed to do. And when lua runs into an error, it ignores the rest of the current chunk: “... whenever an error occurs, Lua ends the current chunk and returns to the application.” (from lua.org) Standalone lua typically sees only one chunk (the file you pass on the command line) but embedded lua implementation often see (sometimes many) more chunks. In luatex’s case, each \directlua is a separate chunk (in ConTeXt, that means every \startluacode block and every \ctxlua call is a separate chunk). The only unusual thing here is that standalone lua silently quits and returns a non-zero exit code to the shell, whereas luatex gives you the typical TeX-style error prompt. The rationale for that is: lua errors can happen in many places in your input file, and if they were silently ignored, your typeset pages could be wrong without you realising it. And to answer your question above: I did not have to try or guess. I know about how assert() works because it is documented in the lua manual (and as it closely mimics the assert() C function, that is easy for me to remember). Best wishes, Taco ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___
Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
On Mon, Oct 14, 2019 at 09:26:58PM +0200, Taco Hoekwater wrote:
> Hi,
>
> > On 14 Oct 2019, at 21:08, Rudolf Bahr wrote:
> >
> >
> > 2. But in the case of an not existing file (BBB.lua) the known error
> > message comes up
> > again:
> > "token call, execute: [ctxlua]:8: /home/sam/context-tests/BBB.lua: No
> > such file or
> >directory".
> >This, of course, is true, but shouldn't be mentioned in an error message!
>
> If you do not want the error message, don’t use assert(). You can just do
>
> f = io.open(...)
> If f then ... else ... end
>
> Best wishes,
> Taco
Hi Taco!
Thank you again for your message!
My wish isn't to avoid error messages, if they are justified! In the case of my
MWE
I want to have a decision in my \startluacode ... \stopluacode environment,
whether
a certain file exists or not. With this decision I want to branch in my program
and
with an error message I cannot do it.
Lua is a wonderfull programming language and I'm appreciative to get a way to
exit
ConTeXt, run Lua code and enter the ConTeXt program at the same location again!
On
the other side, in the last days I spent some time to eliminate errors in my
\startluacode ...\stopluacode program to change code which causes no error
messages
in pure Lua.
Now to your suggestion not to use "assert ()". Indeed it's a solution! My
program
works! I append again its output (again just for fun!). Did you really try it or
has it been just an idea? The MWE is now as follows:
===
\startluacode
userdata = userdata or {}
function userdata.file_exists (name)
local name = name
local f= io.open ( name, "r" )
if f then
f:close ()
context ( name )
context ( " exists!" )
else
context ( name )
context ( " doesn't exist!" )
end
end
\stopluacode
\starttext
\def\lookupfile#1%
{\ctxlua{userdata.file_exists([==[#1]==])}}
\lookupfile{/home/sam/context-tests/AAA.lua}% "AAA.lua" intentionally does
exist
\par
\lookupfile{/home/sam/context-tests/BBB.lua}% "BBB.lua" intentionally
doesn't exist
\stoptext
===
R. Ierusalimschy encourages the use of "assert()". But it is apparantly better
not to
use it under certain circumstances as in \startluacode ... \stopluacode as I've
learnt
now.
Can I avoid therefore Hans' prefix resolvers code?
Best wishes,
Rudolf
is-file.pdf
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Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
Hi, > On 14 Oct 2019, at 21:08, Rudolf Bahr wrote: > > > 2. But in the case of an not existing file (BBB.lua) the known error message > comes up > again: > "token call, execute: [ctxlua]:8: /home/sam/context-tests/BBB.lua: No such > file or >directory". >This, of course, is true, but shouldn't be mentioned in an error message! If you do not want the error message, don’t use assert(). You can just do f = io.open(...) If f then ... else ... end Best wishes, Taco ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___
Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
On Mon, Oct 14, 2019 at 07:19:53PM +0200, Hans Hagen wrote:
> On 10/14/2019 6:50 PM, Rudolf Bahr wrote:
> > THis MWE must be faulty, but where is the error?
> >
> >
> >
> > \startluacode
> >
> > userdata = userdata or {}
> >
> > function userdata.file_exists (name)
> >
> > local name = name
> > local f= assert ( io.open ( name, "r" ))
> >
> > if f then
> >f:close ()
> >context ( name )
> >context ( " exists!" )
> > else
> >context ( name )
> >context ( " doesn't exist!" )
> > end
> > end
> >
> > \stopluacode
> >
> >
> > \starttext
> >
> > \def\lookupfile#1%
> > {\ctxlua{userdata.file_exists([==[#1]==])}}
> >
> > \lookupfile{"$HOME/context-tests/AAA.lua"} % "AAA.lua" intentionally does
> > exist
> > \lookupfile{"$HOME/context-tests/BBB.lua"} % "BBB.lua" intentionally
> > doesn't exist
> >
> > \stoptext
> >
> >
> >
> > It makes no difference in commenting out the first or the second
> > "\lookupfile" command.
> > The error message eventually is always nearly the same:
> >
> > token call, execute: [ctxlua]:8: "$HOME/context-tests/AAA.lua": No such
> > file or directory
> > token call, execute: [ctxlua]:8: "$HOME/context-tests/BBB.lua": No such
> > file or directory
Joseph, Taco and Hans, I thank you very much for your quick answers!
I shall try Hans' interesting suggestion on prefix resolvers after I've studied
it,
for which I certainly need some time!
But before doing so I've a comment:
Your answers, Joseph, Taco and Hans, could lead to the impression, that giving
up
"double quotes as part of file names" and/or "$HOME" in the MWE would be the
solution.
And indeed, not using "double quotes" and "expanding $HOME" by hand partly
brings success:
1. In the case of an existing file (AAA.lua) the MWE works without error
message!
I will append the output-pdf-file here (just for fun!).
2. But in the case of an not existing file (BBB.lua) the known error message
comes up
again:
"token call, execute: [ctxlua]:8: /home/sam/context-tests/BBB.lua: No such
file or
directory".
This, of course, is true, but shouldn't be mentioned in an error message!
Within \startluacode ... \stopluacode it seems one has to abandon the normal
lua world,
at least partly. Are there other "special features"?
Rudolf
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Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
On 10/14/2019 6:50 PM, Rudolf Bahr wrote:
Dear List!
THis MWE must be faulty, but where is the error?
\startluacode
userdata = userdata or {}
function userdata.file_exists (name)
local name = name
local f= assert ( io.open ( name, "r" ))
if f then
f:close ()
context ( name )
context ( " exists!" )
else
context ( name )
context ( " doesn't exist!" )
end
end
\stopluacode
\starttext
\def\lookupfile#1%
{\ctxlua{userdata.file_exists([==[#1]==])}}
\lookupfile{"$HOME/context-tests/AAA.lua"}% "AAA.lua" intentionally does
exist
\lookupfile{"$HOME/context-tests/BBB.lua"}% "BBB.lua" intentionally doesn't
exist
\stoptext
It makes no difference in commenting out the first or the second "\lookupfile"
command.
The error message eventually is always nearly the same:
token call, execute: [ctxlua]:8: "$HOME/context-tests/AAA.lua": No such file or
directory
token call, execute: [ctxlua]:8: "$HOME/context-tests/BBB.lua": No such file or
directory
You're in a tex environment, so no $HOME expansion. You can use the
prefix resolvers:
\startluacode
function userdata.file_exists(name)
local name = name and resolvers.resolve(name)
if name and lfs.isfile(name) then
context("file %a exists",name)
else
context("file %a doesn't exist",name)
end
end
\stopluacode
\starttext
% \def\lookupfile#1{\ctxlua{userdata.file_exists([==[#1]==])}}
\def\lookupfile{\ctxlua{userdata.file_exists(tokens.scanners.string())}}
\lookupfile{home:context-tests/AAA.lua}{xx}
\lookupfile{home:context-tests/BBB.lua}{xx}
\stoptext
-
Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-
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Re: [NTG-context] \ctxlua and \startluacode ... \stopluacode
Hi,
> On 14 Oct 2019, at 18:51, Rudolf Bahr wrote:
>
>
> Dear List!
>
> THis MWE must be faulty, but where is the error?
>
> ===
> \lookupfile{"$HOME/context-tests/AAA.lua"}% "AAA.lua" intentionally does
> exist
$HOME is an actual literal here, since io.open() does not call out to a shell?
Taco
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