Felix "targets" people that would like to use Haskell or Ocaml but have a ton of code in C and C++ to interface with. Felix is a C++ upgrade: it discard the syntax, but retains ABI compatibility, at quite some cost to things like safety for example.

Felix is more or less guaranteed to perform on par with C/C++ or better for the simple reason you can embed C++ directly into Felix, this works because Felix generates C++. And of course you can link to your favourite libraries with minimal syntax.

  type mytype = "My::Type";
  ctor mytype : int = "My::Type ($1)";
  fun addup : mytype * mytype -> mytype = "$1.addup($2)";