Introduce explicit and implicit braces

[muzimuzhi]

Adding an introduction to explicit (tokens having catcode 1 and 2) and implicit (tokens having catcode 1 and 2 or let to such characters) braces can help make the syntax of commands accepting a <general text> (like \detokenize) and relationship between {₁/}₂ and \bgroup/\endgroup more accurate.

Currently in TeX in a Nutshell v0.9,

• On page 16, \detokenize <expandafters> {<text>} is documented that

  The expand processor does full expansion here until an opening brace {₁ is found.

  But actually \detokenize\bgroup<text>} is also syntactically correct here (and for anywhere <general text> is accepted).

• On page 26, it reads

  \bgroup and \egroup are equivalents to {₁ and }₂.

  That's not 100% true, for example \detokenize{<text>\egroup is wrong syntax.

TeX by Topic introduces explicit and implicit braces in sec. 36.3.3 "{} and <left brace><right brace>".

[olsak]

The introduction text of TeX in a Nutshell reads: "The main goal of this document is its brevity. So features are described only roughly and sometimes inaccurately here." I mean that the mention of obscure syntax like \uppercase \bgroup ...} is not needed here. I never used something like that during my three decades of using TeX.