[tex-k] TeXbook: typo in answer to exercise 20.7

[Karl Berry]

    In TeXbook, answer to exercise 20.7, it is written that TeX says:

Can you send me your test input file please?

    which is different from {

You left off the previous and following bits of the sentence (on page
329) which make it make sense:
  
  ... [_1, which is different from {_1 ...

(where ASCII "_" means a typeset subscript).

Knuth is explaining that a left-bracket character with catcode 1
is different from a left-brace character with catcode 1, as far as
argument delimiters go. This is not true for all catcodes, as he also
explains. --thanks, karl.