[texhax] \halign in terms of macro

[Reinhard Kotucha]

On 21 July 2009 Vafa Khalighi wrote:

 > Is it possible to define the control sequence \semihalign with
 > macro programming which behaves exactly like \halign but in its
 > definition \halign is not used at all.

There must be a reason Knuth decided to provide a primitive rather
than a macro, while he even didn't provide primitives for such basic
things like loops.

However, recently I had the great pleasure to meet Klaus Lagally, the
author of ArabTeX.  I'll never forget his words:

  "You can do everything in TeX.  TeX is a Turing machine, ...
  ... and it can be programmed as conveniently as a Turing machine."[1]

This obviously describes your problem very well.

Regards,
  Reinhard

PS: If you intend to buy a Turing machine (a hardware implementation
    by Aarhus University, Denmark), this is what you are looking for:

    http://www.youtube.com/watch?v=cYw2ewoO6c4


[1] Original wording, as far as I remember: "In TeX kann man alles
    machen.  TeX ist eine Turing-Maschine.  Und es lässt sich genauso
    bequem programmieren wie eine Turing-Maschine."

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