> [...] since Knuth highly values the reproducibility of the output of all versions of TeX, any changed version must not be called TEX, TeX, or anything confusingly similar.

I have heard that to be the reason that some don't want to "fix" TeX/LaTeX.

Source: http://en.wikipedia.org/wiki/TeX#License

LaTeX also has a similar clause (or whatever you call it): http://en.wikipedia.org/wiki/LaTeX_Project_Public_License#Un...

To be clear, it is allowed to be called a TeX if it passes a testsuite:

> To enforce this rule, any implementation of the system must pass a test suite called the TRIP test[39] before being allowed to be called TeX

I don't think that there is any particular problem in the code base. Its design, however, has been made with 1970s constraints in mind.

A lot of people have thought about rewriting (parts) of TeX, but the amount of legacy is so high and you have to keep compatibility with lots of existing user code.

So you don't think there is a problem in the code base, but you say: " legacy code is so high and you have to keep compatibility with lots of existing user code". That's a contradiction.

I mean that the code works perfectly in the sense that the behaviour conforms to the specification, but it is hard to modify it. So, there's a problem with the code base, just one that is not visible if you don't want to extend the program (one can argue that it's the worst kind of problem).

There are (at least) XeLaTeX, pdfTeX, and LuaTeX. There's also ConTeXt, which is not LaTeX compatible, extending TeX in a different direction.

I have tried all extensively (except ConTeXt), what I can tell you is that I now use LuaLateX, because it's the natural successor to the other implementations, which have all a really hard time with unicode, ie. with "→" and many other unicode characters. I know about different hacks like embedding a pdf document with the required symbols etc. but that's just reflecting how ignorant the LaTeX architecture is. The algorithms built-in may be clever, but the actual code-base and annual release-cycle is archaic and unmaintainable. The cross-dependencies are so deep, that updating one small package could break anything anytime. Spaghetti-Code Deluxe. Guess why no distribution ships "tlmgr" - the TeX package-manager.

I'm thankful for anything that helps to free us from the *TeX compilers. It's surely hyped too much. Do you believe me when I say that just because you wrote a document with LaTeX, it isn't auto-magically typographically perfect? Look for PDF Documents compiled with LaTeX, many of them have really ugly Typography, because people love to customize things to their own likings and many LaTeX templates even force ugly Typography on their users.