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: 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 ! _115 to _116
      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 _180 to _181
       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 _182
     Goal arity 4: rewrite [what is the text of [theory tennis]] to _182
  Got clause: say [_301 is tasty !]
    Clause unifies to: say [_301 is tasty !]
    gdash: user says [what is tasty]
  Goal arity 3: user says [what is tasty]

No solution```