[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

RE: Interpreter for a subset of Knuth's MMIX in pure XSLT

• To: "'Rich Salz'" <rsalz@d...>,"'Sean McGrath'" <sean.mcgrath@p...>
• Subject: RE: Interpreter for a subset of Knuth's MMIX in pure XSLT
• From: "Michael Kay" <michael.h.kay@n...>
• Date: Tue, 1 Apr 2003 17:03:15 +0100
• Cc: <xml-dev@l...>
• Importance: Normal
• In-reply-to: <3E89AF5F.60102@d...>
• Reply-to: <michael.h.kay@n...>

> > As an exercise in XSLT programming, we in Propylon have 
> implemented a
> > MMIX Interperter 
> (http://www-cs-faculty.stanford.edu/> ~knuth/mmix.html) 
> > in pure XSLT.
> 

What was the design objective for this program?

If it was to be as unreadable as possible and as slow as possible at the
same time, while still failing to produce correct results, then I think
it has probably been achieved. I would think Don Knuth would be
absolutely appalled.

As far as I can see, the program only accesses the first child element
in the source file, namely <babylon>3.125</babylon>. It produces the
answer 3.14159. If the first element is changed, e.g. to 3.126, the
answer changes to 3.15044. If it is changed to 3.11, the answer is NaN.
Any similarity to pi appears to be purely coincidental.

What exactly do these ghastly expressions such as 

round(*****-round(***)+ *** + *** +round(*******) - *** +
(*-(round(***)-floor(***))*floor(***)))"

actually do?

And why, if the idea was to produce an interpreter, have you designed it
so the program to be interpreted has to be hard coded in XSLT, rather
than being read from a data file?

Michael Kay

• Follow-Ups:
  • RE: Interpreter for a subset of Knuth's MMIX in pureXSLT
    • From: Elliotte Rusty Harold <elharo@m...>
  • Re: Interpreter for a subset of Knuth's MMIX in pure XSLT
    • From: Mike Champion <mc@x...>
  • RE: Interpreter for a subset of Knuth's MMIX in pure XSLT
    • From: "Simon St.Laurent" <simonstl@s...>

• References:
  • Re: Interpreter for a subset of Knuth's MMIX in pure XSLT
    • From: Rich Salz <rsalz@d...>

• Prev by Date: Re: Interpreter for a subset of Knuth's MMIX in pure XSLT
• Next by Date: RE: Interpreter for a subset of Knuth's MMIX in pure XSLT
• Previous by thread: Re: Interpreter for a subset of Knuth's MMIX in pure XSLT
• Next by thread: RE: Interpreter for a subset of Knuth's MMIX in pure XSLT
• Index(es):
  • Date
  • Thread