operator: to-upper

    description:
        to-upper |x>
        set all characters to upper case 
        
        to-upper[i1, i2, ... , in] |x>
        change i'th characters to upper case
         
    examples:
        to-upper |fred>
            |FRED>
        
        to-upper[1] |fred>
            |Fred>
      
        to-upper[1,3,5] |abcdefg>
            |AbCdEfg>
    
    see also:
        to-lower