local fn FlattenList( list as Str255 ) as Str255
  long   i
  Str255 flatStr, commaStr

  flatStr = ""
  for i = 1 to len$(list)
    if ( instr$( 0, "[] ,", mid$( list, i, 1 ) ) === 0 )
      flatStr += commaStr + mid$( list, i, 1 )
      commaStr = ", "
    end if
  next
end fn = flatStr

window 1, @"Flatten a list", ( 0, 0, 350, 150 )

print "["; fn FlattenList( "[[1], 2, [[3,4], 5], [[[]]], [[[6]]], 7, 8 []]" ); "]"

HandleEvents