[luatex] Luatex primitive names

[Hans Hagen]

Heiko Oberdiek wrote:
> On Tue, Mar 10, 2009 at 06:36:28PM -0500, Karl Berry wrote:
> 
>> Taco (or anyone) -- is there some simple Lua function which returns some
>> engine identification?
>>
>> I'm thinking of something like
>> \directlua{tex.engine_ident()}  (sorry, wrong syntax, I know),
>> which both luatex and xetex could implement.
>>
>> (I concur with the opinions of only exposing \directlua.)
> 
> I don't unless I have misunderstood something:
> 
> \directlua{...} generates an error message for older versions,
> because it requires a number for the lua state.
> In newer versions the number shouldn't be given, because it
> would cause a deprecation warning -- users always complain
> about warnings. Thus the version information is already
> needed at TeX level before switching to Lua.

we're talking of version 0.40 and onwards and the new syntax will be in 0.40

we don't care about < 0.40 and macro package support before 0.40

also, the syntax will not change that much as we will likely use the 
number as alternative for the name directive (index in array then) so 
that the syntax wil become

\dirextlua
   [name {error message string}]
   [optional number refering to error number string in table]

so, for pre 0.40 it means that the number is basically ignored

> * Version information for each feature/primitive, when
>   it was introduced and when changes occur.

at some point we will declare primitives/features stable (will happen 
stepwise) and the manual will mention it for each (class of) primitives

> It would help macro programmers to write robuster code
> without studying old announcements and logs of the version control
> system.

when functionality changes there will be either new primitives or 
mechanisms to control the behaviour (in pdftex we had several hz variants)

Hans



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