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    "<p style=\"float: left;\"><a href=\"compound-types.ipynb\" target=\"_blank\">Previous</a></p>\n",
    "<p style=\"float: right;\"><a href=\"implicit-parameters.ipynb\" target=\"_blank\">Next</a></p>\n",
    "<p style=\"text-align:center;\">Tour of Scala</p>\n",
    "<div style=\"clear: both;\"></div>\n",
    "\n",
    "# Self-type\n",
    "Self-types are a way to declare that a trait must be mixed into another trait, even though it doesn't directly extend it. That makes the members of the dependency available without imports.\n",
    "\n",
    "A self-type is a way to narrow the type of `this` or another identifier that aliases `this`. The syntax looks like normal function syntax but means something entirely different.\n",
    "\n",
    "To use a self-type in a trait, write an identifier, the type of another trait to mix in, and a `=>` (e.g. `someIdentifier: SomeOtherTrait =>`)."
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     "text": [
      "real Beyoncé: Just spilled my glass of lemonade\n"
     ]
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       "defined \u001b[32mtrait\u001b[39m \u001b[36mUser\u001b[39m\n",
       "defined \u001b[32mtrait\u001b[39m \u001b[36mTweeter\u001b[39m\n",
       "defined \u001b[32mclass\u001b[39m \u001b[36mVerifiedTweeter\u001b[39m\n",
       "\u001b[36mrealBeyoncé\u001b[39m: \u001b[32mVerifiedTweeter\u001b[39m = ammonite.$sess.cmd0$Helper$VerifiedTweeter@36bbcf25"
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    "trait User {\n",
    "  def username: String\n",
    "}\n",
    "\n",
    "trait Tweeter {\n",
    "  this: User =>  // reassign this\n",
    "  def tweet(tweetText: String) = println(s\"$username: $tweetText\")\n",
    "}\n",
    "\n",
    "class VerifiedTweeter(val username_ : String) extends Tweeter with User {  // We mixin User because Tweeter required it\n",
    "\tdef username = s\"real $username_\"\n",
    "}\n",
    "\n",
    "val realBeyoncé = new VerifiedTweeter(\"Beyoncé\")\n",
    "realBeyoncé.tweet(\"Just spilled my glass of lemonade\")  // prints \"real Beyoncé: Just spilled my glass of lemonade\""
   ]
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   "source": [
    "Because we said `this: User =>` in `trait Tweeter`, now the variable `username` is in scope for the `tweet` method. This also means that since `VerifiedTweeter` extends `Tweeter`, it must also mix-in `User` (using `with User`).\n",
    "<p style=\"float: left;\"><a href=\"compound-types.ipynb\" target=\"_blank\">Previous</a></p>\n",
    "<p style=\"float: right;\"><a href=\"implicit-parameters.ipynb\" target=\"_blank\">Next</a></p>\n",
    "<p style=\"text-align:center;\">Tour of Scala</p>\n",
    "<div style=\"clear: both;\"></div>"
   ]
  }
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