Warning: Variable denominator only occurs once in file euclid.dl at line 61
    head = [0,denominator].
--------------^-------------
Warning: Variable denominator only occurs once in file euclid.dl at line 130
    head = [0,denominator].
--------------^-------------
Warning: Variable denominator only occurs once in file euclid.dl at line 134
    head = [numerator,denominator], numerator!=0.
----------------------^---------------------------
