/* $DOC$
   $AUTHOR$
      Copyright 1999 Chen Kedem <niki@actcom.co.il>
   $TEMPLATE$
      Function
   $NAME$
      ReadVar()
   $CATEGORY$
      API
   $SUBCATEGORY$
      User interface
   $ONELINER$
      Return variable name of current GET or MENU
   $SYNTAX$
      ReadVar( [<cVarName>] ) --> cOldVarName
   $ARGUMENTS$
      <cVarName> is a new variable name to set.
   $RETURNS$
      ReadVar() return the old variable name. If no variable previously
      was set, ReadVar() return "".
   $DESCRIPTION$
      ReadVar() is set inside a READ or `MENU TO` command to hold the
      uppercase name of the GET / `MENU TO` variable, and re-set back to old
      value when those commands finished. You should not normally set a
      variable name but rather use it to retrieve the name of a GET
      variable when executing a VALID or WHEN clause, or during `SET KEY`
      execution and you are inside a READ or `MENU TO`.
   $EXAMPLES$
      #include "inkey.ch"
      LOCAL What_Is_Bug
      // display a menu, press <F1> to view the MENU TO variable name
      CLS
      @ 1, 10 PROMPT "blood sucking insect that infect beds   "
      @ 2, 10 PROMPT "germ; virus infection                   "
      @ 3, 10 PROMPT "defect; snag; (source of) malfunctioning"
      @ 4, 10 PROMPT "small hidden microphone                 "
      @ 6, 10 SAY "(Press <F1> for a hint)"
      SetKey( K_F1, {|| ShowVar() } )
      MENU TO What_Is_Bug

      STATIC PROCEDURE ShowVar()
         Alert( ReadVar() )  // --> "WHAT_IS_BUG"
         RETURN
   $STATUS$
      R
   $COMPLIANCE$
      ReadVar() works exactly like CA-Cl*pper's ReadKey().

      Note however,
      that the <cVarName> parameter is not documented and used internally
      by CA-Cl*pper.
   $PLATFORMS$
      All
   $FILES$
      Library is core
   $SEEALSO$
      @...GET, @...PROMPT, MENU TO, READ, SetKey(), __AtPrompt(), __MenuTo()
   $END$
 */