(sorry for the repeat Nathan, this was meant to go to the list too) On Thu, May 26, 2016 at 1:43 PM, Nathan Davis <nda...@positronic-solutions.com> wrote: > First off, I should say that you should first consider alternative > approaches before considering the options below. For example, cond seems > well-suited for this particular case: > > > (defn verify-position[pos type] > (cond (nil? pos) true > (or (> pos 90) > (< pos 0)) false > > . > . > . > > :else true))
Yeah, cond is definitely useful here, but not in general. > However, sometimes you really do want imperative-style control flow. Two > possibilities come to mind here: > > Monads (e.g., algo.monads) > Continuations (e.g., pulley.cps) > > In fact, monads and (delimited) continuations are isomorphic. The main > difference is one of view-point -- the essence of monads is the composition > of computations; the essence of continuations is control flow. > > For a monadic approach, I would start with something like the "Maybe" monad, > but add a monadic 'bail' operator (to use your terminology and avoid > conflicting with the common use of 'return' as one of the fundamental > operators on monads). Essentially, 'bail' would be constructed to abort the > "current computation". Then if you implement a function in terms of the > 'bailing' monad (and encapsulate the effect to that function), you can use > 'bail' to effectively return a value from the function at any point in the > computation. > > With continuations, all you need is an "abortive" continuation back to the > call-site of the function. With pulley.cps, this is easily accomplished > using call-cc / let-cc. For example, here's your first example in terms of > let-cc: This was very informative. I'm definitely going to write this down as something to look into. I think there's probably other and better choices for input validation, but I can see this being extremely useful for some of the equipment control work I do. Thank you for the suggestion. -John -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
