Essentially I want to implement the equivalent of this: ```def eval(e: Expression): AST = e match { ...

# getting-started

[Gavin Ray]

Essentially I want to implement the equivalent of this:

def eval(e: Expression): AST = e match {
  case Literal(value) => q"$value"
  case Attribute(name) => q"row.get($name)"
  case Add(left, right) => q"${eval(left)} + ${eval(right)}"
}

[itzik kasovitch]

What's the difference between this and Kotlin string interpolation?

[Gavin Ray]

String interpolation happens at runtime
Scala quasi-quotes don't produce a value, but a typed AST you can compile and evaluate

Codegen like this is critical for performance in compilers and expression evaluators like the query engines in databases

[Gavin Ray]

You also get free optimization by the compiler since the result is an AST and the compiler can further optimize whatever tree is produced if possible

[Gavin Ray]

https://tetzank.github.io/posts/codegen-in-databases/

http://highscalability.com/blog/2016/9/7/code-generation-the-inner-sanctum-of-database-performance.html

[itzik kasovitch]

Got it. Thanks for explaining. Looks interesting.