String manipulation

This one'll have Jari busy updating his FAQ<g>.  I've managed
to figure out how to delete the last character from the end of
a string without calling an external program.  Along the way,
I've stumbled across a couple of bonuses that are part of the
tail-deletion process.

  Bonus 1) How many charcters are there in a given string?  Use
scoring along with the ?? operator.  Count the number of matches
to the dot wildcard charcter.
###############
:0
*  1^1 VAR ?? .
{ }
LENGTH = $=
###############

  Bonus 2) What is the last character of a string?  Or more
generally the last N charcters of a string?  Note the use of
the $ sign below to anchor to end-of-string...

### Last character
:0
* VAR ?? ().*\/.$
{ TAIL=$MATCH }
#################

For last 2 characters use * VAR ?? ().*\/..$
For last 5 characters use * VAR ?? ().*\/.....$
etc, etc.

  Now we get to apply these formulas to strip the last charcter
off a string.  It gets a bit ugly for special cases.  I've
deliberately chosen a worst-case scenario.
  - set VAR="Testing 012301230111"
  - extract last character of VAR, in this case "1" (see above)
  - assign that character to variable TAIL
  - get the longest match that does not end in the TAIL
    character, and store it in HEAD
  - if the last two or more characters in VAR are identical,
    they all get chopped, oops
  - LENGTH(HEAD) plus 1 SHOULD equal LENGTH(VAR).  That is not
    the case when the last 2 (or more) ending characters are
    identical.
  - in that case, call appendrc recursively to stick back an
    appropriate number of TAIL characters.

######## Main file
VAR="Testing 012301230111"

:0
* VAR ?? ().*\/.$
{ TAIL=$MATCH
  :0
  *$ VAR ?? ().*\/.*[^${TAIL}]
  { HEAD=$MATCH
    :0
    * -1^0
    *  1^1 VAR ?? .
    * -1^1 HEAD ?? .
    { TOOSHORT = $=
      INCLUDERC=appendrc
    }
  }
}
#####################

####### appendrc file
:0
* -1^0
*  1^1 VAR ?? .
* -1^1 HEAD ?? .
{
HEAD="${HEAD}${TAIL}"
INCLUDERC=appendrc
}
#####################

-- 
Walter Dnes (Toronto)
<waltdnes(_at_)interlog(_dot_)com>