Author: Stan Eisenstat
Subject: Correction: An amusing test case
Date: Monday, 19 Oct 2020, 11:42:14

Yesterday I posted an important example:

  Here is an example of why you cannot always replace all
  occurrences:
   
    $ echo \$1\$A\$1 | A=\$1 ./mcBash \$A
    (1)$ >> $A$1$A
   
  The input is "$1$A$1\n".  If you replace all occurrences
  of "$A" by its value "$1", giving "$1$1$1\n" and then
  replace all occurrences of "$1" by its value "$A", you
  get "$A$A$A\n", which is incorrect.  If you replace all
  occurrences of "$A" by its value "$1", giving "$1$1$1\n"
  and then replace all occurrences of "$1" by its value "$A",
  you get "$A$A$A\n", which is still incorrect.

The last sentence should have been:

				   ... If you replace all
  occurrences of "$1" by its value "$A", giving "$A$A$A\n"
  and then replace all occurrences of "$A" by its value "$1",
  you get "$1$1$1\n", which is still incorrect.

--Stan-