# Why \(.) is used in section names in tex.web?

Here are some examples of section names in tex.web:

@<Scan for \(m)\.{mu} units and |goto attach_fraction|@>
@<Scan for \(a)all other units and adjust |cur_val| and |f| accordingly; |goto done| in the case of scaled points@>


Why \(.) is used?

I couldn't find a single use of \(.), so I guess you are referring to letters enclosed in \( and ) in general.

The answer can be found in the definition of \( at the beginning of tex.web:

 \def\(#1){} % this is used to make section names sort themselves better


E.g. if we would replace

@<Scan for \(a)all other units and adjust |cur_val| and |f| accordingly; |goto done| in the case of scaled points@>
@<Scan for \(m)\.{mu} units and |goto attach_fraction|@>


with

@<Scan for all other units and adjust |cur_val| and |f| accordingly; |goto done| in the case of scaled points@>
@<Scan for \.{mu} units and |goto attach_fraction|@>


and then tried to sort them, the \.{ would probable sort before all and thertefore reverse the order. This is unexpected because the user only sees the following mu which would come after all, so \(m) and \(a) are introduced which explicitly mark which character should be used for sorting without having another effect.