# [luatex] \lastnamedcs and \begincsname with empty csname

Hans Hagen pragma at wxs.nl
Mon Jan 8 00:38:18 CET 2018

```On 1/7/2018 11:15 PM, David Carlisle wrote:

> Should not \lastnamedcs expand to the token with empty csname after > \csname\endcsname ?
It's by design (an explicit test and nothing done with a null cs, so no
cleanup side effects too) ... btw, it's already tricky enough this code
and we're not going to change such functionality (just like we don't
change other primitives with side effects).

btw, in practice, where expansion is not always the most extensive and
slowest bit of texing, the speed gain is not that large, we mostly save
on building temporary strings internally which for (only) multi byte utf
is taking some time. Of course it can give less code (no repetition and
a few less tokens). One should also realize that there is no stack
involved so nesting can have side effects, not that i ran into many
surprises but there are cases - which by now i forgot - that one can be
bitten in the tail, as usual with tex expansion, rightfully.

Hans

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