null
```
Starting on goal: [think [user says [what is the text of [theory tennis] ?]]] and [say $x]
Goal arity 3: [think [user says [what is the text of [theory tennis] ?]]] and [say $x]
nextSolution
Got clause: _1 and _2
  Clause unifies to: [think [user says [what is the text of [theory tennis] ?]]] and [say $x]
  gdash: think [user says [what is the text of [theory tennis] ?]]
Goal arity 2: think [user says [what is the text of [theory tennis] ?]]
 Got clause: think _7
   Clause unifies to: think [user says [what is the text of [theory tennis] ?]]
  Clause is native.
   gdash: say $x
 Goal arity 2: say $x
  Got clause: say [it's _21 !]
    Clause unifies to: say [it's _21 !]
    gdash: user says [_22 * _23]
  Goal arity 3: user says [_22 * _23]
  Got clause: say [_53 is _54 !]
    Clause unifies to: say [_53 is _54 !]
    gdash: rewrite with theory "add question mark to user input"
  Goal arity 4: rewrite with theory "add question mark to user input"
   Got clause: rewrite with theory _86
     Clause unifies to: rewrite with theory "add question mark to user input"
    Clause is native.
  REW user says $e1 :- ...
Starting on goal: user says _88
Goal arity 3: user says _88
Got clause: user says [what is the text of [theory tennis] ?]
  Clause unifies to: user says [what is the text of [theory tennis] ?]
  gdash: _87 = add question mark ([what is the text of [theory tennis] ?])
Goal arity 6: _87 = add question mark ([what is the text of [theory tennis] ?])
 Got clause: _123 = add question mark (_124)
   Clause unifies to: _87 = add question mark ([what is the text of [theory tennis] ?])
   gdash: _125 = tocons ([what is the text of [theory tennis] ?])
 Goal arity 4: _125 = tocons ([what is the text of [theory tennis] ?])
  Got clause: _142 = tocons (_143)
    Clause unifies to: _125 = tocons ([what is the text of [theory tennis] ?])
   Clause is native.
    gdash: not ([endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]]] ?])
  Goal arity 2: not ([endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]]] ?])
   Got clause: not (_154)
     Clause unifies to: not ([endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]]] ?])
     gdash: endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]]] ?
   Goal arity 3: endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]]] ?
    Got clause: endswithword_c [cons _158 _159] _160
      Clause unifies to: endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]]] ?
      gdash: endswithword_c [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]] ?
    Goal arity 3: endswithword_c [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]] ?
     Got clause: endswithword_c [cons _164 _165] _166
       Clause unifies to: endswithword_c [cons is [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]]] ?
       gdash: endswithword_c [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]] ?
     Goal arity 3: endswithword_c [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]] ?
      Got clause: endswithword_c [cons _170 _171] _172
        Clause unifies to: endswithword_c [cons the [cons text [cons of [cons [theory tennis] [cons ? end]]]]] ?
        gdash: endswithword_c [cons text [cons of [cons [theory tennis] [cons ? end]]]] ?
      Goal arity 3: endswithword_c [cons text [cons of [cons [theory tennis] [cons ? end]]]] ?
       Got clause: endswithword_c [cons _176 _177] _178
         Clause unifies to: endswithword_c [cons text [cons of [cons [theory tennis] [cons ? end]]]] ?
         gdash: endswithword_c [cons of [cons [theory tennis] [cons ? end]]] ?
       Goal arity 3: endswithword_c [cons of [cons [theory tennis] [cons ? end]]] ?
        Got clause: endswithword_c [cons _182 _183] _184
          Clause unifies to: endswithword_c [cons of [cons [theory tennis] [cons ? end]]] ?
          gdash: endswithword_c [cons [theory tennis] [cons ? end]] ?
        Goal arity 3: endswithword_c [cons [theory tennis] [cons ? end]] ?
         Got clause: endswithword_c [cons _188 _189] _190
           Clause unifies to: endswithword_c [cons [theory tennis] [cons ? end]] ?
           gdash: endswithword_c [cons ? end] ?
         Goal arity 3: endswithword_c [cons ? end] ?
          Got clause: endswithword_c [cons _193 end] _193
            Clause unifies to: endswithword_c [cons ? end] ?
            gdash: ?? "!"("4")
          Goal arity 1: ?? "!"("4")
cut -1. Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r7), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end")))))))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r21)), "=", "fromcons", l("()", r7))))))
           Goal arity 0: false
cut 0. Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r7), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end")))))))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r21)), "=", "fromcons", l("()", r7))))))
back to cut point 4
cut: dropping Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r7), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end")))))))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r21)), "=", "fromcons", l("()", r7))))))
cut: dropping Prolog$Goal(car=l("[]", "endswithword_c", Prolog$Var(id=189L, instance=l("[]", "cons", "?", "end")), Prolog$Var(id=190L, instance=Prolog$Var(id=184L, instance=Prolog$Var(id=178L, instance=Prolog$Var(id=172L, instance=Prolog$Var(id=166L, instance=Prolog$Var(id=160L, instance=l("?")))))))), cdr=Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r18), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), r4))))))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r31)), "=", "fromcons", l("()", r18)))))))
cut: dropping Prolog$Goal(car=l("[]", "endswithword_c", Prolog$Var(id=183L, instance=l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end"))), Prolog$Var(id=184L, instance=Prolog$Var(id=178L, instance=Prolog$Var(id=172L, instance=Prolog$Var(id=166L, instance=Prolog$Var(id=160L, instance=l("?"))))))), cdr=Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r19), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", r4)))))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r30)), "=", "fromcons", l("()", r19)))))))
cut: dropping Prolog$Goal(car=l("[]", "endswithword_c", Prolog$Var(id=177L, instance=l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end")))), Prolog$Var(id=178L, instance=Prolog$Var(id=172L, instance=Prolog$Var(id=166L, instance=Prolog$Var(id=160L, instance=l("?")))))), cdr=Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r19), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", r4))))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r29)), "=", "fromcons", l("()", r19)))))))
cut: dropping Prolog$Goal(car=l("[]", "endswithword_c", Prolog$Var(id=171L, instance=l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end"))))), Prolog$Var(id=172L, instance=Prolog$Var(id=166L, instance=Prolog$Var(id=160L, instance=l("?"))))), cdr=Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r19), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", r4)))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r28)), "=", "fromcons", l("()", r19)))))))
cut: dropping Prolog$Goal(car=l("[]", "endswithword_c", Prolog$Var(id=165L, instance=l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end")))))), Prolog$Var(id=166L, instance=Prolog$Var(id=160L, instance=l("?")))), cdr=Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r19), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", r4))), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r27)), "=", "fromcons", l("()", r19)))))))
cut: dropping Prolog$Goal(car=l("[]", "endswithword_c", Prolog$Var(id=159L, instance=l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end"))))))), Prolog$Var(id=160L, instance=l("?"))), cdr=Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r19), "=", "append_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", r4)), l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r26)), "=", "fromcons", l("()", r19)))))))
cut: dropping Prolog$Goal(car=Prolog$Var(id=154L, instance=l("[]", "endswithword_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end")))))))), "?")), cdr=Prolog$Goal(car=l("!", "4"), cdr=Prolog$Goal(car=l("false"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r19), "=", "append_c", r4, l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r24)), "=", "fromcons", l("()", r19)))))))
cut: dropping Prolog$Goal(car=l("[]", "not", l("()", l("[]", "endswithword_c", Prolog$Var(id=125L, instance=l("[]", "cons", "what", l("[]", "cons", "is", l("[]", "cons", "the", l("[]", "cons", "text", l("[]", "cons", "of", l("[]", "cons", l("[]", "theory", "tennis"), l("[]", "cons", "?", "end")))))))), "?"))), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=126L, instance=r16), "=", "append_c", r5, l("[]", "cons", "?", "end")), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=123L, instance=Prolog$Var(id=87L, instance=r21)), "=", "fromcons", l("()", r16)))))
Got 0 rewritten terms.
     gdash: user says _55
   Goal arity 3: user says _55
    Got clause: user says [what is the text of [theory tennis] ?]
      Clause unifies to: user says [what is the text of [theory tennis] ?]
      gdash: rew ! [what is the text of [theory tennis] ?] to [what is _53 ?]
    Goal arity 5: rew ! [what is the text of [theory tennis] ?] to [what is _53 ?]
     Got clause: rew ! _335 to _336
       Clause unifies to: rew ! [what is the text of [theory tennis] ?] to [what is _53 ?]
       gdash: rew [what is the text of [theory tennis] ?] to [what is _53 ?]
     Goal arity 4: rew [what is the text of [theory tennis] ?] to [what is _53 ?]
      Got clause: rew _400 to _401
        Clause unifies to: rew [what is the text of [theory tennis] ?] to [what is _53 ?]
        gdash: rewrite [what is the text of [theory tennis] ?] to _402
      Goal arity 4: rewrite [what is the text of [theory tennis] ?] to _402
       Got clause: rewrite [what is the _439 of _440 ?] to [what is [the _439 of _440] ?]
         Clause unifies to: rewrite [what is the text of [theory tennis] ?] to [what is [the text of [theory tennis]] ?]
         gdash: rew [what is [the text of [theory tennis]] ?] to [what is _53 ?]
       Goal arity 4: rew [what is [the text of [theory tennis]] ?] to [what is _53 ?]
        Got clause: rew _504 to _505
          Clause unifies to: rew [what is [the text of [theory tennis]] ?] to [what is _53 ?]
          gdash: rewrite [what is [the text of [theory tennis]] ?] to _506
        Goal arity 4: rewrite [what is [the text of [theory tennis]] ?] to _506
        Got clause: rew _599 to _599
          Clause unifies to: rew [what is [the text of [theory tennis]] ?] to [what is [the text of [theory tennis]] ?]
          gdash: ?? "!"("6")
        Goal arity 1: ?? "!"("6")
cut -1. Prolog$Goal(car=l("!", "6"), cdr=Prolog$Goal(car=l("[]", Prolog$Var(id=53L, instance=l("[]", "the", Prolog$Var(id=439L, instance=l("text")), "of", Prolog$Var(id=440L, instance=l("[]", "theory", "tennis")))), "is", Prolog$Var(id=54L, instance=r11))))
         Goal arity 3: [the text of [theory tennis]] is _54
          Got clause: [the _606 of _607] is _608
            Clause unifies to: [the text of [theory tennis]] is _54
            gdash: the text of [theory tennis] is _54
          Goal arity 6: the text of [theory tennis] is _54
           Got clause: the text of [theory _624] is _625
             Clause unifies to: the text of [theory tennis] is _54
             gdash: _54 = text of theory tennis
           Goal arity 6: _54 = text of theory tennis
            Got clause: _631 = text of theory _632
              Clause unifies to: _54 = text of theory tennis
             Clause is native.
              gdash: -
SUCCESS!
  solution found in step 247```