Text this: On the diamond operator related to the wave equation

  _____     ______              ______    ______  
 / ____||  /_   _//     ___    /_   _//  /_____// 
/ //---`'   -| ||-     /   ||   -| ||-   `____ `  
\ \\___     _| ||_    | [] ||   _| ||_   /___//   
 \_____||  /_____//    \__ ||  /_____//  `__ `    
  `----`   `-----`      -|_||  `-----`   /_//     
                         `-`             `-`