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POModify a class with typed traits in Scala
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  1. POModify a class with typed traits in Scala
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    copied!<p>I've been playing around with Scala recently, and when working with parser combinators, I kind of had some problems extending them. Basically, what I'm trying to do is something like this.</p> <pre><code>import scala.util.parsing.combinator.RegexParsers abstract class Statement case object Foo extends Statement case object Bar extends Statement case object Baz extends Statement class Program(statements: List[Statement]) class FooBarLanguageParser extends RegexParsers { def program: Parser[Program] = rep(statement) ^^ (v =&gt; new Program(List() ++ v)) def statement: Parser[Statement] = foo|bar def foo: Parser[Statement] = "foo" ^^ (_ =&gt; Foo) def bar: Parser[Statement] = "bar" ^^ (_ =&gt; Bar) } trait BazStatement { this: FooBarLanguageParser =&gt; override def statement: Parser[Statement] = baz|this.statement // inifinite recursion def baz: Parser[Statement] = "baz" ^^ (_ =&gt; Baz) } object Main { def main(args: Array[String]) { val normalFooBar = new FooBarLanguageParser() val fooBarProgram = normalFooBar.parseAll(normalFooBar.program, "foo bar") val extendedFooBar = new FooBarLanguageParser() with BazStatement val extendedFooBarProgram = extendedFooBar.parseAll(extendedFooBar.program, "foo bar baz") println(fooBarProgram.successful) println(extendedFooBarProgram.successful) } } </code></pre> <p>Here, I would like to call <code>FooBarLanguageParser</code>'s <code>statement</code> method in <code>BazStatement</code>, but with the above code I'm recursively calling <code>BazStatement</code>'s method, so no way it would work properly.</p> <p>I already took a look at the answers around, and I know that I could extend the class and use abstract override, or somethink like this, but I don't think it would really make any sense here, as <code>BazStatement</code> is really an additional feature I want to mixin with my basic parser. I definitely don't want to have some random things like </p> <pre><code>object StrangeInheritance extends BazStatement </code></pre> <p>authorized in the code.</p> <p>Would there be any idiomatic way to do this properly in Scala or do I need to think again about the general design of the app?</p>
 

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