# [texhax] Query : why can \ifnum comparison operators not be \let, yet \def is OK ?

David Carlisle d.p.carlisle at gmail.com
Wed Feb 3 11:17:53 CET 2016

"Why?" is hard to answer. That is just how it is.

The comparison syntax needs an explicit < of catcode 12 but macros are
as usual expanded when tex is looking for syntactic forms, so it may
be produced by expanding \def defined macros.
The implicit < token defined by \let is a syntax error because it
isn't a catcode 12 token with character code of < > or =

David