number.format.fmfn

/*
 * =====================================================
 * number.format ( input ; format )
 * 
 * RETURNS:        (string) Formatted input according to format supplied
 * DEPENDENCIES:   none 
 * NOTES:          Adapted from http://www.briandunning.com/cf/769 by Toby Beedell
 * =====================================================
 * 
 */

Let ( [
  var.input = input;
  var.format = format;
  var.valid = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  var.match = "#";
  test.exit = IsEmpty ( var.input ) or IsEmpty ( var.format )

]; 
  If ( test.exit;
    // then
    var.input;
    // else
    Let ( [
      match.count = PatternCount ( var.format; var.match );
      match.none = match.count < 1;
      format.length = Length ( var.format );
      format.end = If ( match.none and format.length > 0 ; var.format )
    ];
      If ( match.none;
        // then
        format.end & var.input;
        // else
        Let ( [
          var.filtered = Filter ( var.input ; var.valid );
          filtered.length = Length ( var.filtered );
          match.position = Position ( var.format ; var.match ; 1 ; 1 );
          var.prefix = If ( match.position ≠ 1 ; Left ( var.format ; match.position - 1 ) );
          format.char = Middle ( var.format ; match.position ; 1 );
          var.char = Left ( var.filtered ; 1 );
          is.upper = IsEmpty ( Filter ( format.char ; var.match ) );
          _tBit = If ( is.upper ; Upper ( var.char ) ; Lower ( var.char ) );
          format.remainder = Right ( var.format ; format.length - match.position );
          input.remainder = Right ( var.filtered ; filtered.length - 1 )
        ];
          var.prefix & _tBit & number.format ( input.remainder ; format.remainder )
        )
      )
    )
  )
)