[luatex] \Udelcodenum as a number

[David Carlisle]

Hi,

The file

----------------------------------------

\Udelcode`a=0 "28
\immediate\write20{\the\Udelcodenum`a}

\Udelcodenum`a= "000028
\immediate\write20{\the\Udelcodenum`a}

\bye


----------------------------------------


produces the error

! You can't use `\Udelcodenum' after \the.

In each case (using TL2015 pretest luatex)

These primitives are documented as being "compatible with xetex", but
xetex does not give an error here and produces

1073741864
40


that is
"40000028 and "28
(I think I'd have expected "28 in both cases, but I'll query that
on xetex list).


Is it intended that \Udelcodenum  can be used to extract the
delcode assigned to a character as a number?

Incidentally if you use \Udelcode rather than \Udelcodenum
in the above you get an error message that implies
\Udelcodenum might work:


! Can't use \Udelcode as a number (try \Udelcodenum).

David

I came across this trying to debug \string in xetex and started
to collect some test files for extended primitives common to
\xetex and luatex here

https://github.com/davidcarlisle/utex
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