[taliesinb]

Yeah, it's pretty easy to turn

    Map[#^2&] /* Select[PrimeQ] /* Select[OddQ] 

into

    Select[OddQ[#] && PrimeQ[#]&] /* Map[#^2&] 

and so on via rules that look like:

    Select[s1_] /* Select[s2_] :> Select[s1[#] && s2[#]&] 
    Map[f_ ? SideEffectFreeQ] /* s_Select :> s /* Map[f]
    Map[Extract[p_Integer | p_Key]] :> Extract[{All, p}]

I'm already doing a bunch of that for Dataset.

But in reality you need to move to a DSL for complex enough rules, and then Clojure and WL will be on the same footing (Clojure even a bit stronger, maybe, WL doesn't really have a proper macro system).

Does Clojure core do or allow for any of that kind of optimization already?

[malisper]

I don't know about Clojure, but Common Lisp provides something called Compiler Macros[0]. They basically allow the programmer to define two versions of a procedure. One that is a macro, and one that is an actual procedure. The macro will expand only at compile time (it can also specify to call the procedure instead of expanding), and the procedure will be called only at run time. I suggest you look at [0] for some examples of how it is possible to optimize something as simple as squaring a number.

[0] http://clhs.lisp.se/Body/m_define.htm