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