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Jsonnet (#5)
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‎build.sbt

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@@ -10,6 +10,7 @@ libraryDependencies ++= Seq(
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"com.lihaoyi" %% "os-lib" % "0.11.4",
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"com.lihaoyi" %% "scalatags" % "0.13.1",
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"com.lihaoyi" %% "cask" % "0.10.2",
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"com.lihaoyi" %% "fastparse" % "3.1.1",
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// Java libraries
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// scraping
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"org.jsoup" % "jsoup" % "1.19.1",

‎src/main/scala/jsonnet/Expr.scala

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package jsonnet
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import jsonnet.Parser.expr
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sealed trait Expr
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object Expr:
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case class Num(value: Int) extends Expr
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case class Str(value: String) extends Expr
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case class Ident(name: String) extends Expr
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case class Plus(left: Expr, right: Expr) extends Expr
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case class Dict(pairs: Map[String, Expr]) extends Expr
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case class Local(name: String, assigned: Expr, body: Expr) extends Expr
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case class Func(argNames: Seq[String], body: Expr) extends Expr
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case class Call(expr: Expr, args: Seq[Expr]) extends Expr
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def evaluate(expr: Expr, scope: Map[String, Value]): Value =
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expr match
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case Expr.Ident(name) => scope(name)
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case Expr.Num(i) => Value.Num(i)
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case Expr.Str(s) => Value.Str(s)
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case Expr.Dict(kvs) => Value.Dict(kvs.map { case (k, v) => (k, evaluate(v, scope)) })
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case Expr.Plus(left, right) =>
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(evaluate(left, scope), evaluate(right, scope)) match
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case (Value.Num(leftNum), Value.Num(rightNum)) => Value.Num(leftNum + rightNum)
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case (Value.Str(leftStr), Value.Str(rightStr)) => Value.Str(leftStr + rightStr)
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case Expr.Local(name, assigned, body) =>
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val assignedValue = evaluate(assigned, scope)
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evaluate(body, scope + (name -> assignedValue))
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case Expr.Call(expr, args) =>
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val Value.Func(call) = evaluate(expr, scope)
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val evaluatedArgs = args.map(evaluate(_, scope))
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call(evaluatedArgs)
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case Expr.Func(argNames, body) =>
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Value.Func(args => evaluate(body, scope ++ argNames.zip(args).toMap))
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// Use this for printing as a compact json string
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private def serialize(v: Value): String =
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v match
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case Value.Num(i) => i.toString
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case Value.Str(s) => s"\"$s\""
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case Value.Dict(kvs) => kvs.map((k, v) => s"\"$k\": ${serialize(v)}").mkString("{", ", ", "}")
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// Use this for pretty printing
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private def serialize2(v: Value): ujson.Value =
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v match
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case Value.Num(i) => ujson.Num(i)
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case Value.Str(s) => ujson.Str(s)
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case Value.Dict(kvs) => ujson.Obj.from(kvs.map { case (k, v) => (k, serialize2(v)) })
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def jsonnet(input: String): String =
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// serialize(evaluate(fastparse.parse(input, expr(_)).get.value, Map.empty))
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ujson.write(
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serialize2(evaluate(fastparse.parse(input, Parser.expr(_)).get.value, Map.empty)),
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indent = 2
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)
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def main(args: Array[String]): Unit = {
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Seq(
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evaluate(fastparse.parse("\"hello\"", expr(_)).get.value, Map.empty),
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evaluate(fastparse.parse("""{ "hello": "world", "key": "value" }""", expr(_)).get.value, Map.empty),
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evaluate(fastparse.parse("\"hello\" + \"world\"", expr(_)).get.value, Map.empty),
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// Call
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evaluate(fastparse.parse("""local greeting = "hello "; greeting + greeting""", expr(_)).get.value, Map.empty),
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evaluate(fastparse.parse("""local x = "Hello "; local y = "World"; x + y""", expr(_)).get.value, Map.empty),
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// evaluate(fastparse.parse("""local greeting = "Hello"; nope + nope""", expr(_)).get.value, Map.empty),
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// Func
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evaluate(fastparse.parse("""local f = function(a) a + "1"; f("123")""", expr(_)).get.value, Map.empty),
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evaluate(
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fastparse
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.parse("""local f = function(a, b) a + " " + b; f("hello", "world")""", expr(_))
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.get
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.value,
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Map.empty
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)
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).foreach(println)
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// jsonnet
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println(jsonnet("""|local greeting = "Hello ";
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|local person = function (name) {
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| "name": name,
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| "welcome": greeting + name + "!"
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|};
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|{
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| "person1": person("Alice"),
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| "person2": person("Bob"),
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| "person3": person("Charlie")
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|}""".stripMargin))
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println(
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jsonnet(
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"""|local bonus = 15000;
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|local person = function (name, baseSalary) {
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| "name": name,
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| "totalSalary": baseSalary + bonus
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|};
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|{"person1": person("Alice", 10000), "person2": person("Bob", 20000)}
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|""".stripMargin
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)
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)
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}
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end Expr

‎src/main/scala/jsonnet/Parser.scala

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package jsonnet
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import fastparse.*
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import MultiLineWhitespace.*
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object Parser:
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def num[p: P]: P[Expr.Num] = P(CharIn("0-9").rep(1).!.map(_.toInt)).map(Expr.Num.apply)
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def str0[p: P]: P[String] = P("\"" ~~/ CharsWhile(_ != '"', 0).! ~~ "\"")
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def str[p: P]: P[Expr.Str] = P(str0).map(Expr.Str.apply)
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def ident0[p: P]: P[String] = P(CharIn("a-zA-Z_") ~~ CharsWhileIn("a-zA-z0-9_", 0)).!
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def ident[p: P]: P[Expr.Ident] = P(ident0).map(Expr.Ident.apply)
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def local[p: P]: P[Expr.Local] = P("local" ~/ ident0 ~ "=" ~ expr ~ ";" ~ expr).map(Expr.Local.apply)
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def func[p: P]: P[Expr.Func] = P("function" ~/ "(" ~ ident0.rep(0, ",") ~ ")" ~ expr).map(Expr.Func.apply)
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def dict[p: P]: P[Expr.Dict] = P("{" ~/ (str0 ~ ":" ~/ expr).rep(0, ",") ~/ "}").map(kvs => Expr.Dict(kvs.toMap))
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def callExpr[p: P]: P[Expr] = P(num | str | dict | local | func | ident)
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def call[p: P]: P[Seq[Expr]] = P("(" ~/ expr.rep(0, ",") ~ ")")
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def prefixExpr[p: P]: P[Expr] = P(callExpr ~ call.rep).map { case (left, items) =>
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items.foldLeft(left)(Expr.Call.apply)
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}
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def plus[p: P]: P[Expr] = P("+" ~ prefixExpr)
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def expr[p: P]: P[Expr] = P(prefixExpr ~ plus.rep).map { case (left, rights) =>
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rights.foldLeft(left)(Expr.Plus.apply)
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}
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def main(args: Array[String]): Unit = {
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Seq( // str
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fastparse.parse("\"hello\"", str(_)),
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fastparse.parse("\"hello world\"", str(_)),
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fastparse.parse("\"\"", str(_)),
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fastparse.parse("123", str(_))
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).foreach(println)
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Seq( // ident
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fastparse.parse("hello", ident(_)),
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fastparse.parse("_world", ident(_)),
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fastparse.parse("hello world", ident(_)),
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fastparse.parse("123", ident(_))
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).foreach(println)
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Seq( // plus
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fastparse.parse("\"hello\" + \"world\"", expr(_)),
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fastparse.parse("\"hello\" + \" \" + \"world\"", expr(_)),
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fastparse.parse("a + b", expr(_)),
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fastparse.parse("""a + " " + c""", expr(_))
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).foreach(println)
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Seq( // dict
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fastparse.parse("""{"a": "b", "cde": id, "nested": {}}""", dict(_)),
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fastparse.parse("""{"a": "A", "b": "bee"}""", expr(_)),
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fastparse.parse("""f()(a) + g(b, c)""", expr(_)),
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fastparse.parse("""local thing = "kay"; { "f": function(a) a + a, "nested": {"k": "v"}}""", expr(_)),
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// Case for exercise 1
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fastparse.parse("""local thing = 100; """, expr(_)),
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fastparse.parse(
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"""|local bonus = 15000;
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|local person = function (name, baseSalary) {
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| "name": name,
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| "totalSalary": baseSalary + bonus
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|};
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|{"person1": person("Alice", 10000), "person2": person("Bob", 20000)}
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|""".stripMargin,
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expr(_)
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)
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).foreach(println)
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}

‎src/main/scala/jsonnet/README.md

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# Jsonnet
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Exercises:
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- Modify our Jsonnet interpreter to be able to handle basic numbers as well ...
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Track `Value.Num` and `Expr.Num`
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- Modify def serialize to ... pretty print the output JSON ...
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See `Expr.serialize2` and its use in `Expr.jsonnet`

‎src/main/scala/jsonnet/Value.scala

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package jsonnet
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sealed trait Value
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object Value:
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case class Str(value: String) extends Value
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case class Num(value: Int) extends Value
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case class Dict(pairs: Map[String, Value]) extends Value
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case class Func(call: Seq[Value] => Value) extends Value
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end Value

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