Converts
            a string that represents a real (floating-point) value into a real
            value
         
         
         The distof and rtos functions are complementary.
            If you pass distof a string created
            by rtos, distof is guaranteed
            to return a valid value, and vice versa (assuming the mode values
            are the same).
         
         Arguments
         
- string
 
            - 
               
                  A string to be converted.
                     The argument must be a string that distof can
                     parse correctly according to the units specified by mode.
                     It can be in the same form that rtos returns,
                     or in a form that AutoCAD allows for keyboard entry. 
                  
                
             - mode
 
            - 
               
                  The units in which the
                     string is currently formatted. The mode corresponds
                     to the values allowed for the AutoCAD system variable LUNITS
                     in the Command Reference. Specify one of
                     the following numbers for mode:
                  
                  1   Scientific
                  
                  2   Decimal
                  
                  3   Engineering
                     (feet and decimal inches)
                  
                  4   Architectural
                     (feet and fractional inches)
                  
                  5   Fractional
                  
                
             
         
         Return Values
         
         A real number, if successful;
            otherwise nil.
         
         NoteThe distof function treats
               modes 3 and 4 the same. That is, if mode specifies
               3 (engineering) or 4 (architectural) units, and string is in
               either of these formats, distof returns
               the correct real value.