why lua?

why lua?

[Jonas Stein]

i'd like to make a small presentation for friends about
context. 
Why do we use lua and not python or perl or...
Where can i find the features for lua for this job?

Kind regards,

-- 
Jonas Stein <news@jonasstein.de>

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Re: why lua?

[Martin Schröder]

2010/12/17 Jonas Stein <news@jonasstein.de>:
> Why do we use lua and not python or perl or...
> Where can i find the features for lua for this job?

RTFAQ: http://www.luatex.org/faq.html

HTH. HAND.
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Re: why lua?

[Philipp A.]

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2010/12/17 Jonas Stein <news@jonasstein.de>

> i'd like to make a small presentation for friends about
> context.
> Why do we use lua and not python or perl or...
>

you can. google for “luatex lunatic”.
you’ll have to build a little module defining the macros you use, though.
(like \ctxpython, \directpython and so on)

Where can i find the features for lua for this job?
>
> Kind regards,
>
> --
> Jonas Stein <news@jonasstein.de>
>

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Re: why lua?

[Hans Hagen]

On 17-12-2010 4:20, Jonas Stein wrote:
> i'd like to make a small presentation for friends about
> context.
> Why do we use lua and not python or perl or...
> Where can i find the features for lua for this job?

you can find arguments in presentations and articles and mk.pdf

- nice language (pascal like, nu obscure $characters, tolerant spacing)
- easy to learn and no complex concepts
- good manual that covers all
- mature when we started using it
- small footprint and no truckload of libs to carry along (packaging tex 
is already enough work)
- pretty fast and efficient
- no feature creep, proper academic research project, tightly managed
- it fits tex pretty well
- designed with embedding in mind
- most of all: we like it

(I first ran into lua when I was playing with scite's extension 
mechanism and immediately thought of how nice it would be to have it in 
tex. Hartmut made the first variant that gave access to registers and 
provided printing to tex, then Taco stepped in and fundamental opening 
up started etc etc etc)

Hans

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Re: why lua?

[Hans Hagen]

On 17-12-2010 11:35, Philipp A. wrote:
> 2010/12/17 Jonas Stein<news@jonasstein.de>
>
>> i'd like to make a small presentation for friends about
>> context.
>> Why do we use lua and not python or perl or...
>>
>
> you can. google for “luatex lunatic”.
> you’ll have to build a little module defining the macros you use, though.
> (like \ctxpython, \directpython and so on)
>
> Where can i find the features for lua for this job?

In what sense? Context core code will never use \ctxpython, \ctxruby, 
\ctxperl, so it will be module specific as one cannot depend on 
libraries being on the system, at least not before luatex is stabelized. 
Btw, I'm not sure if Luigi made a module for it (if he still uses python 
at all).

Hans

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Re: why lua?

[Philipp Gesang]

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On 2010-12-17 <16:20:31>, Jonas Stein wrote:
> i'd like to make a small presentation for friends about
> context. 
> Why do we use lua and not python or perl or...
> Where can i find the features for lua for this job?

After all those arguments in favor of Lua the only thing I can
add are valid reasons against using python for embedding:
  http://twistedmatrix.com/users/glyph/rant/extendit.html
and concerning perl ;)
  http://lua-users.org/lists/lua-l/2010-02/msg00934.html

Regards, Philipp


> 
> Kind regards,
> 
> -- 
> Jonas Stein <news@jonasstein.de>
> 
> ___________________________________________________________________________________
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> 
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Re: why lua?

[Hans Hagen]

On 18-12-2010 12:27, Philipp Gesang wrote:
> On 2010-12-17<16:20:31>, Jonas Stein wrote:
>> i'd like to make a small presentation for friends about
>> context.
>> Why do we use lua and not python or perl or...
>> Where can i find the features for lua for this job?
>
> After all those arguments in favor of Lua the only thing I can
> add are valid reasons against using python for embedding:
>    http://twistedmatrix.com/users/glyph/rant/extendit.html
> and concerning perl ;)
>    http://lua-users.org/lists/lua-l/2010-02/msg00934.html

Ah .. the extending vs the embedding debate ... well, an argument could 
have been that we don't want to extend python -)

I've only used Pascal, Modula2, Perl (after all that compiling and 
linking I loved the scripting aspect but the language ... well ...), 
Ruby (brought me back happy Modula memories but it got so huge and had 
incompatible updates but is still my second choice), but I feel quite 
happy with Lua now.

Anyhow, I don't like languages that need religious arguments to become 
popular.

Hans


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Re: why lua?

[Philipp A.]

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hans, some of the things you said are a bit unclear to me:

2010/12/18 Hans Hagen <pragma@wxs.nl>

>  Ah .. the extending vs the embedding debate ... well, an argument could
> have been that we don't want to extend python -)
>

see last paragraphs.

I've only used Pascal, Modula2, Perl (after all that compiling and linking I
> loved the scripting aspect but the language ... well ...), Ruby (brought me
> back happy Modula memories but it got so huge and had incompatible updates
> but is still my second choice), but I feel quite happy with Lua now.
>

give python a try. i love it because it has the writability of perl without
(de)referencing and funny symbols, and a class system like java/c++/… (no
prototyping and stuff)

well, i just like it. and since i don’t know lua (well, that’s not exactly
true, but i can’t write a normal sized script without looking things up),
and tend to do things like i would do them in other languages i know. e.g.:
how do you loop elegantly over table values? “for k,v in pairs(t) do print(v)
end” creates a throwaway variable k, which doesn’t seem right. some things
are totally counter-intuitive for me like tables beginning with index 1, and
so on.

so i guess it’s natural that i would like to use a scripting language i know
and like, like python.

Anyhow, I don't like languages that need religious arguments to become
> popular.


like… which one? i only know of the tabs vs. spaces and vim vs. emacs
religious wars. i can’t remember of any languages being subdued to that.

or are you talking about lua having been invented at a catholic university
and thus being a product of a sect somehow?

Hans
>

what i want to show you is kross<http://en.wikipedia.org/wiki/Kross_%28KDE%29>
.
kross is the project for bringing consistent scripting to KDE, and it is
just awesome, since it allows you to write stuff in the scripting language
of your choice.

my dream for luatex/context would be a built-in lua interpreter (because lua
is so fucking small) and optional modules for other, heavier, scripting
languages (perl, ruby), which you don’t have to install. i don’t care if
python is embedded or extended, i just want to write \directpython{for num
in [9,2,4,8]: ctx.print(num**3)} (or sth. like that)

but don’t get me wrong, i love context and luatext, i just like other
languages better than lua (you weren’t content with latex and created
context, so this shouldn’t be alien to you)

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Re: why lua?

[Aditya Mahajan]

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On Sat, 18 Dec 2010, Philipp A. wrote:

> my dream for luatex/context would be a built-in lua interpreter (because lua
> is so fucking small) and optional modules for other, heavier, scripting
> languages (perl, ruby), which you don’t have to install. i don’t care if
> python is embedded or extended, i just want to write \directpython{for num
> in [9,2,4,8]: ctx.print(num**3)} (or sth. like that)

luatex is more than lua (or any prog/scripting language) embedded in tex; 
it is a programming language with acess to tex's internals. For example, 
you can find the dimension of each node in a vlist and use a different 
line-breaking algorithm or tweak the node list after line breaking is done 
(something like this is done in arabic line-breaking). If you do not 
want easy access to tex's internals, embedding/extending tex is relatively 
easy: see for example perltex. Whether the binary of the prog language is 
embedded in the tex binary, or in the wrapper script for calling tex is 
immaterial. On the other hand, if you want acess to tex's internals, you 
can either code it for a specific language (like luatex does), or provide 
an API interface to the internals. My understanding is that given the 
complexity of the tex codebase, the latter was more too much effort for 
too little gain. After all, python vs lua is a minor difference, compared 
to the programing abilities of TeX.

Aditya

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Re: why lua?

[luigi scarso]

On Fri, Dec 17, 2010 at 11:51 PM, Hans Hagen <pragma@wxs.nl> wrote:
> On 17-12-2010 11:35, Philipp A. wrote:
>>
>> 2010/12/17 Jonas Stein<news@jonasstein.de>
>>
>>> i'd like to make a small presentation for friends about
>>> context.
>>> Why do we use lua and not python or perl or...
>>>
>>
>> you can. google for “luatex lunatic”.
>> you’ll have to build a little module defining the macros you use, though.
>> (like \ctxpython, \directpython and so on)
>>
>> Where can i find the features for lua for this job?
>
> In what sense? Context core code will never use \ctxpython, \ctxruby,
> \ctxperl, so it will be module specific as one cannot depend on libraries
> being on the system, at least not before luatex is stabelized. Btw, I'm not
> sure if Luigi made a module for it
no ( but can be interesting )
>(if he still uses python at all).
yes, for plone

-- 
luigi
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Re: why lua?

[Philipp Gesang]

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On 2010-12-18 <01:50:29>, Philipp A. wrote:

<snip lines="some"/>

> well, i just like it. and since i don’t know lua (well, that’s not exactly
> true, but i can’t write a normal sized script without looking things up),
> and tend to do things like i would do them in other languages i know. e.g.:
> how do you loop elegantly over table values? “for k,v in pairs(t) do print(v)
> end” creates a throwaway variable k, which doesn’t seem right. some things

Depending on whether you want to access the non-hashed content as
well you might want to use the “next” iterator instead as it’s
slightly faster (according to my tests, that is). You won’t get
around the local variable, though; I have no clue and no time to
check if it’s even technically feasible to iterate a hash table
without accessing the hashes.

> are totally counter-intuitive for me like tables beginning with index 1, and
> so on.

Feels natural after some time, I guarantee. And you’ll never look
the same way at a fencepost again …

What you’ll miss most is all the nice shortcuts and syntactic
sugar like “setdefault(k,[]).append(v)” (two lines in Lua) and
the lazy handling of arrays, strings &c. as sequences that can be
iterated over like it was all the same, and probably the error
handling. Nothing you can’t live without.

> > Anyhow, I don't like languages that need religious arguments to become
> > popular.

> or are you talking about lua having been invented at a catholic university
> and thus being a product of a sect somehow?

Never looked at it that way. There should be a “fun facts”
section on the wiki to list all the confusing mysteries
surrounding context.

Regards,
Philipp


PS:

> kross is the project for bringing consistent scripting to KDE, and it is
> just awesome, since it allows you to write stuff in the scripting language
> of your choice.

Apart from being OT, you can always switch to a window manager
that uses your favorite scripting language instead -- mine has
Lua inside which is a lot cleaner than doing configuration in
e.g. bash or something.



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Re: why lua?

[Taco Hoekwater]

Hi,

On 12/18/2010 01:50 AM, Philipp A. wrote:
>
> like… which one? i only know of the tabs vs. spaces

The significant whitespace is why python would not have been
an option for the core extension language in luatex even if
it was twice as small and twice as fast as lua. Forced indentation
simply does not work out well if data and program are intermixed
in the same source file.

Which is not saying that I don't like python, but (also taking account
the other differences to lua) it is simply the wrong tool for the job.

> my dream for luatex/context would be a built-in lua interpreter (because
> lua is so fucking small) and optional modules for other, heavier,
> scripting languages (perl, ruby), which you don’t have to install.

An extended version of luatex-lunatic (or some similar project) would
potentially allow that. A lot of the lua functions that 'talk' to the
internals are nothing more than wrappers for argument and return value
grabbing, and it would be pretty easy to (re)code those bindings for
any other scripting language.

The remaining functions that are not trivially implemented are the
ones that we need to work on before 1.0, because these are the exactly
the areas where the TeX source is too messy to be easily interfaced,
in any scripting language.


Best wishes,
Taco
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Re: why lua?

[Hans Hagen]

On 18-12-2010 12:03, Philipp Gesang wrote:
> On 2010-12-18<01:50:29>, Philipp A. wrote:
>
> <snip lines="some"/>
>
>> well, i just like it. and since i don’t know lua (well, that’s not exactly
>> true, but i can’t write a normal sized script without looking things up),
>> and tend to do things like i would do them in other languages i know. e.g.:
>> how do you loop elegantly over table values? “for k,v in pairs(t) do print(v)
>> end” creates a throwaway variable k, which doesn’t seem right. some things
>
> Depending on whether you want to access the non-hashed content as
> well you might want to use the “next” iterator instead as it’s
> slightly faster (according to my tests, that is). You won’t get
> around the local variable, though; I have no clue and no time to
> check if it’s even technically feasible to iterate a hash table
> without accessing the hashes.

indeed, for k, v in next, sometable do ... is faster as it saves one 
function call (i.e. pairs returning the next, table)

for indexed iteration using for i=1,n do ... is much faster than ipairs 
as it involves no function calls

>> are totally counter-intuitive for me like tables beginning with index 1, and
>> so on.
>
> Feels natural after some time, I guarantee. And you’ll never look
> the same way at a fencepost again …

indeed, I also like the start at 1 very much, as you say .. natural

> What you’ll miss most is all the nice shortcuts and syntactic
> sugar like “setdefault(k,[]).append(v)” (two lines in Lua) and
> the lazy handling of arrays, strings&c. as sequences that can be
> iterated over like it was all the same, and probably the error
> handling. Nothing you can’t live without.

and often you can roll out your own without carying the truckload of 
(mostly soon forgotten) lib code

>>> Anyhow, I don't like languages that need religious arguments to become
>>> popular.
>
>> or are you talking about lua having been invented at a catholic university
>> and thus being a product of a sect somehow?
>
> Never looked at it that way. There should be a “fun facts”
> section on the wiki to list all the confusing mysteries
> surrounding context.

I was refering to python related religious (with the programming 
language being the gospel) discussions, so far I never ran into a lua 
one. All those 'one should use this language over that' or 'this 
operating system over that one' are wasted on me as languages come and 
go, as do operating systems and related concepts. Pointless discussions 
when seen over a 1000 year period of time. Printing used to be done 
using wooden blocks and that was high end and the best at some point, 
then came lead (too poisonous now), then film (short fashion), now ...

> Regards,
> Philipp
>
>
> PS:
>
>> kross is the project for bringing consistent scripting to KDE, and it is
>> just awesome, since it allows you to write stuff in the scripting language
>> of your choice.

like .net

> Apart from being OT, you can always switch to a window manager
> that uses your favorite scripting language instead -- mine has
> Lua inside which is a lot cleaner than doing configuration in
> e.g. bash or something.

sure, and performance seldom is an issue I guess on todays machines.

Hans

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Re: why lua?

[Hans Hagen]

On 18-12-2010 1:50, Philipp A. wrote:

> but don’t get me wrong, i love context and luatext, i just like other
> languages better than lua (you weren’t content with latex and created
> context, so this shouldn’t be alien to you)

Sure, it's just that the core of context will be tex/lua only as it 
needs to be portable and mixing languages will not help at that level.

Probably the best way to use other languages in applications of context 
/ luatex is to do something lunatic that luigi did, the overhead of 
wrapping is probably neglectable. We can look into that around luatex 
version 1.0.

For me personally the only reason to look into pyton (or ruby or perl or 
php or ...) would be that it's needed in a project but so far i never 
had such projects i.e. could choose my own languages (so it was ruby at 
some point and lua now). Who knows what the future brings.

Hans

ps. I once read about Icon as language and somehow that one also had 
some appeal. I never had a running environment. Smalltalk is also nice, 
esp the (original) books (esp the historic one), and Lisp (in relation 
to tex) also has some appeal. Live is too short to learn all those 
languages and stay fluent in them, i.e. one simply forgets a lot when 
usage zeros.

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               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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Re: why lua?

[Philipp Gesang]

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On 2010-12-18 <12:35:38>, Hans Hagen wrote:
> On 18-12-2010 12:03, Philipp Gesang wrote:
> >Depending on whether you want to access the non-hashed content as
> >well you might want to use the “next” iterator instead as it’s
> >slightly faster (according to my tests, that is). You won’t get
> >around the local variable, though; I have no clue and no time to
> >check if it’s even technically feasible to iterate a hash table
> >without accessing the hashes.
> 
> indeed, for k, v in next, sometable do ... is faster as it saves one
> function call (i.e. pairs returning the next, table)
> 
> for indexed iteration using for i=1,n do ... is much faster than
> ipairs as it involves no function calls

Well, according to a quick test using “next” with hash tables has
only a *very* slight advantage (in time) over pairs. With arrays
the difference to ipairs() is much higher; in mixed arrays/hashes
it might turn out even higher.

For tables I came up with this relation (“<” meaning less
execution time than):
  while < for < repeat < next < ipairs
where “repeat … until” and “while … do … end” check if the final
index has been reached. But the difference between the three
loops is rather neglegible.

What always baffled me is that in the manual Roberto advertises
ipairs() as the iterator of choice (at least in the v.5.0 doc).
Compared to the other options using it is just, well, erratic.

Regard, Philipp


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Re: why lua?

[luigi scarso]

On Sat, Dec 18, 2010 at 2:04 PM, Hans Hagen <pragma@wxs.nl> wrote:
> ps. I once read about Icon as language and somehow that one also had some
> appeal. I never had a running environment. Smalltalk is also nice, esp the
> (original) books (esp the historic one),
it's easy to try squeak
http://www.squeak.org/


>and Lisp (in relation to tex) also
> has some appeal.
True, see
http://www.nongnu.org/skribilo/
(there is also a context support)
A binding  to libguile should be no difficult to achieve.

>Live is too short to learn all those languages and stay
> fluent in them, i.e. one simply forgets a lot when usage zeros.
we should start to think how to to become immortal.


-- 
luigi
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Re: why lua?

[Hans Hagen]

On 18-12-2010 2:06, Philipp Gesang wrote:

> What always baffled me is that in the manual Roberto advertises
> ipairs() as the iterator of choice (at least in the v.5.0 doc).
> Compared to the other options using it is just, well, erratic.

I did lots of testing (an doptimizing) in critical code but in practice 
one will not notice much difference in a mkiv run. Actually, I changed 
all pairs, ipairs as there was a temporary intention to remove them from 
the lua core.

btw, in for i=1,#t do ... the #t is also a function call (so having many 
in these t[#t+1] = ... cases is also slower but again, seldom noticeable 
as lua in general is so fast

a similar dicussion can be held for strings being hashed but again the 
penalty is neglectable esp if one takes into account that strings only 
have one instance and compare real fast (pointer comparison); in mkiv / 
luatex we have lots of strings (keys, identical values, etc) and it 
really pays off to have them hashed

Hans

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Re: why lua?

[Hans Hagen]

On 18-12-2010 2:18, luigi scarso wrote:

> True, see
> http://www.nongnu.org/skribilo/
> (there is also a context support)
> A binding  to libguile should be no difficult to achieve.

ah, interesting ... we should have a sort of reference context document 
with some structure, itemize, tables, graphics etc and then see how it 
would code in different languages that way (one problem is lazy 
evaluation in function arguments, so it might be that lisp is the best 
variant).

Hans

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Re: why lua?

[Philipp Gesang]

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On 2010-12-18 <14:20:46>, Hans Hagen wrote:
> On 18-12-2010 2:06, Philipp Gesang wrote:
> 
> >What always baffled me is that in the manual Roberto advertises
> >ipairs() as the iterator of choice (at least in the v.5.0 doc).
> >Compared to the other options using it is just, well, erratic.
> 
> I did lots of testing (an doptimizing) in critical code but in
> practice one will not notice much difference in a mkiv run.
> Actually, I changed all pairs, ipairs as there was a temporary
> intention to remove them from the lua core.
> 
> btw, in for i=1,#t do ... the #t is also a function call (so having

My fault, I just forgot about that; with the array size stored in
a local variable the “for” loop is faster than “while”, as
expected.

> many in these t[#t+1] = ... cases is also slower but again, seldom
> noticeable as lua in general is so fast

… when adding to an array the “t[#t+1] = elm” approach turns out
to be still faster than table.insert() which, again, is
advertised in the manual. Even python’s append() method is faster
than table.insert() and that means a lot.

Philipp

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Re: why lua?

[Hans Hagen]

On 18-12-2010 3:17, Philipp Gesang wrote:

> … when adding to an array the “t[#t+1] = elm” approach turns out
> to be still faster than table.insert() which, again, is
> advertised in the manual. Even python’s append() method is faster
> than table.insert() and that means a lot.

seems to be faster in upcoming 5.2

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