FWIW, the Scala folks have done something along these lines, Value Classes, originally aka Inline Classes.<div> <div><a href="https://docs.google.com/document/d/10TQKgMiJTbVtkdRG53wsLYwWM2MkhtmdV25-NZvLLMA/edit?hl=en_US&pli=1">https://docs.google.com/document/d/10TQKgMiJTbVtkdRG53wsLYwWM2MkhtmdV25-NZvLLMA/edit?hl=en_US&pli=1</a> <div class="gmail_quote">On Mon, Aug 27, 2012 at 12:58 PM, Neil Toronto <<a href="mailto:neil.toronto@gmail.com" target="_blank">neil.toronto@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div class="im">On 08/27/2012 09:11 AM, Vincent St-Amour wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> TR's complex number optimizations eliminate repeated boxing and unboxing in chains of operations that each consume and produce complex numbers. Similar optimizations for structs would eliminate structs for intermediate results in chains of operations that each consume and produce that same (single) kind of struct. If your code has such chains of operations, then these optimizations could apply. Do you have code that you think would benefit that I could look at? </blockquote> </div> Not yet. I've given up on a union of different probability representation types for now. For arrays, I could. An array is just a function with a finite, rectangular domain (a "shape"). Think of the type like this: (struct: (A) array ([shape : (Vectorof Index)] [proc : ((Vectorof Index) -> A)])) (This is a bit simplified.) So (array-exp (array-abs arr)) doesn't actually compute (log (abs x)) for any `x', it just creates an array that would if you asked it for an element. IOW, it's equivalent to (array-map (compose exp abs) arr) which itself is equivalent to (array (array-shape arr) (compose exp abs (array-proc arr))) If I made functions like `array-exp' and `array-map' into macros, and if array structs were unboxed, Racket's optimizer could inline the compositions. I imagine this eventual lovely outcome: (let ([proc (array-proc arr)]) (array (array-shape arr) (lambda (x) (unsafe-flexp (unsafe-flabs (proc x)))))) There are also FlArray and FCArray, which are subtypes of Array that store their elements (unboxed in flvectors and fcvectors). FlArray-specific operations are currently about 5x faster than Array's. But Array's ops don't allocate stores for intermediate results, so with the right optimizations, Array's could be the faster ones. If you want to have a look right now, checkout <a href="https://github.com/ntoronto/racket.git" target="_blank">https://github.com/ntoronto/racket.git</a> and try this program: #lang typed/racket (require math/array) (define arr (array [[1.2 4.0] [3.2 -1.8]])) (inline-array-map exp (inline-array-map abs arr))<div class="HOEnZb"><div class="h5"> Neil ⊥ _________________________ Racket Developers list: <a href="http://lists.racket-lang.org/dev" target="_blank">http://lists.racket-lang.org/dev</a> </div></div></blockquote></div> </div></div>