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 "drop question mark from user input"

  Goal arity 4: rewrite with theory "drop question mark from user input"

   Got clause: rewrite with theory _86

     Clause unifies to: rewrite with theory "drop question mark from user input"

    Clause is native.

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 = drop question mark ([what is the text of [theory tennis]])

Goal arity 6: _87 = drop question mark ([what is the text of [theory tennis]])

 Got clause: _123 = drop question mark (_124)

   Clause unifies to: _87 = drop 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: endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] end]]]]]] ?

  Goal arity 3: endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] end]]]]]] ?

   Got clause: endswithword_c [cons _147 _148] _149

     Clause unifies to: endswithword_c [cons what [cons is [cons the [cons text [cons of [cons [theory tennis] end]]]]]] ?

     gdash: endswithword_c [cons is [cons the [cons text [cons of [cons [theory tennis] end]]]]] ?

   Goal arity 3: endswithword_c [cons is [cons the [cons text [cons of [cons [theory tennis] end]]]]] ?

    Got clause: endswithword_c [cons _153 _154] _155

      Clause unifies to: endswithword_c [cons is [cons the [cons text [cons of [cons [theory tennis] end]]]]] ?

      gdash: endswithword_c [cons the [cons text [cons of [cons [theory tennis] end]]]] ?

    Goal arity 3: endswithword_c [cons the [cons text [cons of [cons [theory tennis] end]]]] ?

     Got clause: endswithword_c [cons _159 _160] _161

       Clause unifies to: endswithword_c [cons the [cons text [cons of [cons [theory tennis] end]]]] ?

       gdash: endswithword_c [cons text [cons of [cons [theory tennis] end]]] ?

     Goal arity 3: endswithword_c [cons text [cons of [cons [theory tennis] end]]] ?

      Got clause: endswithword_c [cons _165 _166] _167

        Clause unifies to: endswithword_c [cons text [cons of [cons [theory tennis] end]]] ?

        gdash: endswithword_c [cons of [cons [theory tennis] end]] ?

      Goal arity 3: endswithword_c [cons of [cons [theory tennis] end]] ?

       Got clause: endswithword_c [cons _171 _172] _173

         Clause unifies to: endswithword_c [cons of [cons [theory tennis] end]] ?

         gdash: endswithword_c [cons [theory tennis] end] ?

       Goal arity 3: endswithword_c [cons [theory tennis] end] ?

        Got clause: endswithword_c [cons _177 _178] _179

          Clause unifies to: endswithword_c [cons [theory tennis] end] ?

          gdash: endswithword_c end ?

        Goal arity 3: endswithword_c end ?

Exception in native class main$RewriteWithTheory: java.lang.NullPointerException

	at main$Prolog.Trail_Undo(main.java:167)

	at main$Prolog.rewriteWith(main.java:943)

	at main$RewriteWithTheory.yo(main.java:1422)

	at main$Prolog$BaseNative.yo(main.java:841)

	at main$Prolog.step(main.java:561)

	at main$Prolog.nextSolution(main.java:682)

	at main$Prolog.solve(main.java:657)

	at main$Prolog.solve(main.java:661)

	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.lang.reflect.Method.invoke(Method.java:497)

	at main.call(main.java:861)

	at main.queryAI(main.java:184)

	at main.answer(main.java:135)

	at sun.reflect.GeneratedMethodAccessor2251.invoke(Unknown Source)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.lang.reflect.Method.invoke(Method.java:497)

	at main.callOpt(main.java:543)

	at main.callStaticAnswerMethod(main.java:842)

	at main.answer(main.java:438)

	at sun.reflect.GeneratedMethodAccessor3594.invoke(Unknown Source)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.lang.reflect.Method.invoke(Method.java:497)

	at main.callOpt(main.java:1896)

	at main.callStaticAnswerMethod(main.java:2193)

	at main.callDehBots(main.java:740)

	at main.answerImpl(main.java:729)

	at main.answer(main.java:781)

	at main$Channel.tendTo(main.java:131)

	at main.slackBotLoop(main.java:312)

	at main.main(main.java:948)

	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.lang.reflect.Method.invoke(Method.java:497)

	at x30.callOpt(x30.java:4547)

	at x30.callMain(x30.java:3405)

	at x30.runMainMethod(x30.java:1509)

	at x30.runProgramQuick(x30.java:1488)

	at x30.runProgram(x30.java:1428)

	at x30.javax2(x30.java:1155)

	at x30.javaxmain(x30.java:269)

	at x30.goMain(x30.java:195)

	at x30.main(x30.java:82)

Native clause fails

No solution```