If the above file is typeset with ConTeXt alone it stops with the error message:

! Missing number, treated as zero.

<to be read again>

                   ∞

l.9 \catcode`√∞

               =\active \def√∞{^^F0}

?

Process aborted

If the line \show ð is uncommented in the above file, then XeConTeXt stops with this error message:

[]\*12ptrmtf* and what does

@\par via @@0 b=0 p=-10000 d=100

@@1: line 1.2- t=100 -> @@0

{vertical mode: \show}

> ð=macro:

->^^F0.

l.14 \show ð

            

?

Process aborted

Best regards: OK