investigate ways to reduce `Sto` clutter

[mhuesch]

an example of troublesome-looking Sto output:

        924 : CellThunk(Ev { _: VClosure(Name("x"), App(App(Prim(Add), Lit(LInt(1))), Var(Name("acc"))), {Name("_1"): VRef(0), Name("acc"): VRef(923), Name("foldl"): VRef(3)}) })
        925 : CellThunk(UnevExpr { expr: App(Prim(Head), Var(Name("xs"))), env: {Name("_1"): VRef(0), Name("acc"): VRef(118), Name("f"): VRef(116), Name("foldl"): VRef(2), Name("xs"): VRef(120)} })
        926 : CellRedirect(VRef(110))
        927 : CellThunk(Ev { _: VClosure(Name("x"), App(App(Prim(Add), Lit(LInt(1))), Var(Name("acc"))), {Name("_1"): VRef(0), Name("acc"): VRef(926), Name("foldl"): VRef(3)}) })
        928 : CellThunk(UnevExpr { expr: App(Prim(Head), Var(Name("xs"))), env: {Name("_1"): VRef(0), Name("acc"): VRef(110), Name("f"): VRef(108), Name("foldl"): VRef(2), Name("xs"): VRef(112)} })
        929 : CellRedirect(VRef(102))
        930 : CellThunk(Ev { _: VClosure(Name("x"), App(App(Prim(Add), Lit(LInt(1))), Var(Name("acc"))), {Name("_1"): VRef(0), Name("acc"): VRef(929), Name("foldl"): VRef(3)}) })
        931 : CellThunk(UnevExpr { expr: App(Prim(Head), Var(Name("xs"))), env: {Name("_1"): VRef(0), Name("acc"): VRef(102), Name("f"): VRef(100), Name("foldl"): VRef(2), Name("xs"): VRef(104)} })
        932 : CellRedirect(VRef(95))
        933 : CellThunk(Ev { _: VClosure(Name("x"), App(App(Prim(Add), Lit(LInt(1))), Var(Name("acc"))), {Name("_1"): VRef(0), Name("acc"): VRef(932), Name("foldl"): VRef(3)}) })
        934 : CellThunk(UnevExpr { expr: App(Prim(Head), Var(Name("xs"))), env: {Name("_1"): VRef(0), Name("acc"): VRef(95), Name("f"): VRef(93), Name("foldl"): VRef(2), Name("xs"): VRef(97)} })
        935 : CellRedirect(VRef(87))
        936 : CellThunk(Ev { _: VClosure(Name("x"), App(App(Prim(Add), Lit(LInt(1))), Var(Name("acc"))), {Name("_1"): VRef(0), Name("acc"): VRef(935), Name("foldl"): VRef(3)}) })
        937 : CellThunk(UnevExpr { expr: App(Prim(Head), Var(Name("xs"))), env: {Name("_1"): VRef(0), Name("acc"): VRef(87), Name("f"): VRef(85), Name("foldl"): VRef(2), Name("xs"): VRef(89)} })

we see a lot of duplication and (most concerning to me), it appears as though currying-by-default means we cannot strip down the env of a closure.

this comes from a length computation across a large list:

defn foldl
 (fix (lam [foldl]
   (lam [f acc xs]
     (if (null xs)
       acc
       (foldl
         f
         (f acc (head xs))
         (tail xs)))))))

(defn length (foldl (lam [acc x] (+ 1 acc)) 0))

if we had an uncurried language, we'd be able to see that (lam [acc x] (+ 1 acc)) has no free variables and therefore doesn't need an environment. instead, because we are currying, that represents two lambdas, and the variable is "free" inside the body of the inner lambda, because it was bound by the outer (or maybe I have the order switched up).

this makes me think that currying-by-default is worth reconsidering.