The Algol 60 code in http://gtoal.com/languages/algol60/mcelan/ was extracted from the
listing (at page 29 onwards) in the PDF file at https://ir.cwi.nl/pub/9085/9085D.pdf

I believe this is a general purpose macro processor, which is being used
to extend the assembly language for the X8 computer.

More info on the MC ELAN1 assembler is at https://ir.cwi.nl/?next=2280#filter=all:elan

In particular, the document https://ir.cwi.nl/pub/9144/9144D.pdf contains more source code.

Some context was missing from the mcelan source but it all looks like things that an X8
programmer will probably recognise.  I added some stubs at the start of the listing to
allow it to compile with the JFF Algol 60 compiler.  These should be removed...