Hello all, I'm working on something that involves HLists where I'm making use of the hUpdateAtHNat function for array-like semantics, which works great if you know the index of the element you want at compile time: Prelude> :module +Data.HList Prelude Data.HList> let hl = hEnd $ hBuild "foobar" 123 True Loading [a bunch of packages] Prelude Data.HList> hl H["foobar", 123, True] Prelude Data.HList> hUpdateAtHNat hZero 90909 hl H[90909, 123, True] Prelude Data.HList> hUpdateAtHNat (hSucc hZero) 90909 hl H["foobar", 90909, True] Prelude Data.HList> hUpdateAtHNat (hSucc $ hSucc hZero) 90909 hl H["foobar", 123, 90909] So far so good. What's giving me trouble is figuring out how to update at an arbitrary index, where that index is only known at runtime, because hZero and hSucc are of different types: Prelude Data.HList> :t hZero hZero :: Proxy 'HZero Prelude Data.HList> :t hSucc hZero hSucc hZero :: Proxy ('HSucc 'HZero) What I'd ideally like is some kind of function intToHNatProxy that would take an Int and return a Proxy of the appropriate type, but I so far only kinda sorta understand how proxies and lifted types work, so I haven't yet succeeded in constructing one. Any advice would be very welcome. Thanks, Phil