Friday, August 15, 2014

Scala pros and cons from F# dev view

Recently I started to learn Scala (for about 2 weeks now). Here is prons and cons so far (note: I've not written any serious code yet, just have read "Scala for the impatient" and now reading "Programming in Scala" by Odersky):


  • Passing not evaluated block as argument ("by-name arguments". Allows to develop better DSLs)
  • Macros!
  • There are few libraries written with macros, impossible to implement in a language like c# or f# (MacWire etc.)


  • No not-nullable types (this is a huge one)
  • Not whitespace sensitive (curly braces everywhere) 
  • No type inference for arguments and, sometimes, for result type (signatures involving generic types may be really hairy) 
  • No compiler warning on implicitly discarded expression value (possibly wrong code like => x * 2); => x * 3). The result of the first map is discarded silently. In contrast, F# forces us to write arr |> (fun x -> x * 2) |> ignore; arr |> (fun x -> x * 3).

Wednesday, August 13, 2014

STM revisited: add Scala

Some time ago I compared F# and Haskell STM implementation performance. Today I'm adding Scala into it:

So, it's more than two times slower than Haskell, but more than 3 times faster than F#. Interesting.

Sunday, August 10, 2014

Duck typing in Scala

Scala keeps surprising me. It has much good stuff that F# has. For example, I believed that statically resolved type parameters are unique to F#. Turns out this is not the case. Scala has equivalent feature called "structural types". It has nice syntax compared to F#'s statically resolved type parameters. However, it uses reflection under the hood while F# uses inlining to instantiate functions in-place at compile time. This approach should definitely have awful performance characteristics. Surprisingly, it's not the case:

Static call took about 0.5 seconds, "duck typing" call took about 4 seconds. It only 8-10 times slower than static call. Frankly, I expected something like 100x - 1000x degradation. So, it's not as fast as the equivalent feature in F#, but it certainly practically useful in many circumstances.