Strtolst (AutoLISP function)

;;;WIKI-STRTOLST
;;;Parses a string into a list of fields.
;;;Usage: (wiki-strtolst
;;;         [InputString containing fields]
;;;         [FieldSeparatorWC field delimiter wildcard string
;;;          Use "`," for comma and " ,\t" for white space
;;;         ]
;;;         [TextDelimiter text delimiter character.]
;;;         [EmptyFieldsDoCount flag.
;;;           If nil, consecutive field delimiters are ignored.
;;;           Nil is good for word (white space) delimited strings.
;;;         ]
;;;       )
;|
   Edit the source code for this function at 

  http://autocad.wikia.com/wiki/Strtolst

|;
;;;Avoid cleverness.
;;;Human readability trumps elegance and economy and cleverness here.
;;;This should be readable to a programmer familiar with any language.
;;;In this function, I'm trying to honor readability in a new (2008) way.
;;;And I am trying a new commenting style.
;;;Tests
;;;(alert (apply 'strcat (mapcar '(lambda (x) (strcat "\n----\n" x)) (wiki-strtolst "1 John,\"2 2\"\" pipe,\nheated\",3 the end,,,,," "`," "\"" nil))))
;;;(alert (apply 'strcat (mapcar '(lambda (x) (strcat "\n----\n" x)) (wiki-strtolst "1 John,\"2 2\"\" pipe,\nheated\",3 the end,,,,," "`," "\"" T))))
(DEFUN
   WIKI-STRTOLST (INPUTSTRING FIELDSEPARATORWC TEXTDELIMITER
                  EMPTYFIELDSDOCOUNT / CHARACTERCOUNTER CONVERSIONISDONE
                  CURRENTCHARACTER CURRENTFIELD CURRENTFIELDISDONE
                  FIRSTCHARACTERINDEX PREVIOUSCHARACTER RETURNLIST
                  TEXTMODEISON
                 )
  ;;Initialize the variables for clarity's sake
  (SETQ
    ;;For the AutoLISP (substr string index length) function, the first character index is 1
    FIRSTCHARACTERINDEX 1
    ;;We start the character counter one before the beginning
    CHARACTERCOUNTER
     (1- FIRSTCHARACTERINDEX)
    PREVIOUSCHARACTER ""
    CURRENTCHARACTER ""
    CURRENTFIELD ""
    CURRENTFIELDISDONE NIL
    TEXTMODEISON NIL
    CONVERSIONISDONE NIL
    RETURNLIST NIL
  )
  ;;Make sure that the FieldSeparatorWC is not empty.
  (COND
    ;;If an empty string matches the FieldSeparatorWC,
    ((WCMATCH "" FIELDSEPARATORWC)
     ;;Then
     ;;1. Give an alert about the problem.
     (ALERT
       ;;Include princ to allow user to see and copy error
       ;;after dismissing alert box.
       (PRINC
         (STRCAT
           "\n\""
           FIELDSEPARATORWC
           "\" is not a valid field delimiter."
         )
       )
     )
     ;;2. Exit with error.
     (EXIT)
    )
  )
  ;;Start the main character-by-character InputString examination loop.
  (WHILE (NOT CONVERSIONISDONE)
    (SETQ
      ;;Save CurrentCharacter as PreviousCharacter.
      PREVIOUSCHARACTER
       CURRENTCHARACTER
      ;;CharacterCounter is initialized above to start 1 before first character.  Increment it.
      CHARACTERCOUNTER
       (1+ CHARACTERCOUNTER)
      ;;Get new CurrentCharacter from InputString.
      CURRENTCHARACTER
       (SUBSTR INPUTSTRING CHARACTERCOUNTER 1)
    )
    ;;Decide what to do with CurrentCharacter.
    (COND
      ;;If
      ((AND
         ;;there is a TextDelimiter,
         (/= TEXTDELIMITER "")
         ;;and CurrentCharacter is a TextDelimiter,
         (= CURRENTCHARACTER TEXTDELIMITER)
       )
       ;;then
       ;;1.  Toggle the TextModeIsOn flag
       (IF (NOT TEXTMODEISON)
         (SETQ TEXTMODEISON T)
         (SETQ TEXTMODEISON NIL)
       )
       ;;2.  If this is the second consecutive TextDelimiter character, then
       (IF (= PREVIOUSCHARACTER TEXTDELIMITER)
         ;;Output it to CurrentField.
         (SETQ CURRENTFIELD (STRCAT CURRENTFIELD CURRENTCHARACTER))
       )
      )
      ;;Else if CurrentCharacter is a FieldDelimiter wildcard match,
      ((WCMATCH CURRENTCHARACTER FIELDSEPARATORWC)
       ;;Then
       (COND
         ;;If TextModeIsOn = True, then 
         ((= TEXTMODEISON T)
          ;;Output CurrentCharacter to CurrentField.
          (SETQ CURRENTFIELD (STRCAT CURRENTFIELD CURRENTCHARACTER))
         )
         ;;Else if
         ((OR ;;EmptyFieldsDoCount, or
              (= EMPTYFIELDSDOCOUNT T)
              ;;the CurrentField isn't empty,
              (/= "" CURRENTFIELD)
          )
          ;;Then
          ;;Set the CurrentFieldIsDone flag to true.
          (SETQ CURRENTFIELDISDONE T)
         )
         (T
          ;;Else do nothing
          ;;Do not flag the CurrentFieldDone,
          ;;nor output the CurrentCharacter.
          NIL
         )
       )
      )
      ;;Else if CurrentCharacter is empty,
      ((= CURRENTCHARACTER "")
       ;;Then
       ;;We are at the end of the string.
       ;;1.  Flag ConversionIsDone.
       (SETQ CONVERSIONISDONE T)
       ;;2.  If
       (IF (OR ;;EmptyFieldsDoCount, or
               EMPTYFIELDSDOCOUNT
               ;;the PreviousCharacter wasn't a FieldSeparatorWC, or
               (NOT (WCMATCH PREVIOUSCHARACTER FIELDSEPARATORWC))
               ;;the ReturnList is still nil due to only empty non-counting fields in string,
               ;;(Added 2008-02-18 TGH. Bug fix.)
               (= RETURNLIST NIL)
           )
         ;;Then flag the CurrentFieldIsDone to wrap up the last field.
         (SETQ CURRENTFIELDISDONE T)
       )
      )
      ;;Else (CurrentCharacter is something else),
      (T
       ;;Output CurrentCharacter to CurrentField.
       (SETQ CURRENTFIELD (STRCAT CURRENTFIELD CURRENTCHARACTER))
      )
    )
    ;;If CurrentFieldIsDone,
    (IF CURRENTFIELDISDONE
      ;;Then
      ;;Output it to the front of ReturnList.
      (SETQ
        RETURNLIST
         (CONS CURRENTFIELD RETURNLIST)
        ;;Start a new CurrentField.
        CURRENTFIELD
         ""
        CURRENTFIELDISDONE NIL
      )
    )
    ;;End the main character-by-character InputString examination loop.
  )
  ;;Reverse the backwards return list and we are done.
  (REVERSE RETURNLIST)
)