Just for clarity, here's an example using `set!` and `define`, although I wouldn't really suggest this style:
#lang typed/racket (: f : Real -> Real) (define (f x) (define rand-value (random)) (define new-value (+ x rand-value)) (set! new-value (- new-value x)) new-value) Sam On Wed, Jul 5, 2017 at 10:52 PM, Alasdair McAndrew <[email protected]> wrote: > Well, after a bit of fiddling, I've discovered I can indeed do what I need > to, with a judicious use of "let" for creating a swag of random values, and > ensuring that their use is all within the scope of let. So far, all good! > > On Thursday, 6 July 2017 10:54:53 UTC+10, Royall Spence wrote: >> Sounds like two questions wrapped into one. When it comes to setting >> names to values, Scheme programming encourages the use of a "let" >> expression to bind values to names inside of a (usually narrow) scope >> rather than assigning a value to a variable. See more here: >> https://docs.racket-lang.org/guide/let.html >> >> As for the typed random value, the Flonum from (random) should be fine >> since a Flonum is also a Real. Can you provide a short example of >> runnable code that exposes the problem you're having? >> >> On Wed, Jul 5, 2017, at 08:39 PM, Alasdair McAndrew wrote: >> > I'm doing a little programming which requires the use of some random >> > numbers. Basically I add a random value at one stage, and subtract it a >> > bit later. Something like this pseudo-code (where "x" is an existing >> > variable): >> > >> > set rand_value <- (random) >> > set new_value <- x + rand_value >> > >> > ... do stuff ... >> > >> > set new_value <- new_value - rand_value >> > >> > All values may be considered Reals. I tried to do this in Typed Racket, >> > where x was of type "Real" and got errors about mismatched types: >> > "(random)" produces a "flonum". I was also using "set!" for the >> > assignment of the random value, which I understand to be poor practice: >> > how would I do something like the above in a more "rackety" manner? >> > Thank you! >> > >> > -- >> > You received this message because you are subscribed to the Google Groups >> > "Racket Users" group. >> > To unsubscribe from this group and stop receiving emails from it, send an >> > email to [email protected]. >> > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
