tdantas: It's certainly a powerful mechanism you've made. Sometimes scotch is too much and a beer will do. In general highly generic, parameterized code can be hard to maintain

I kind of loathe reading code where you have to think about what the parameters, which are functions, take

That aside, I have frequently written a pipeline-esque function, like your chain, but that handles stopping early, rather than running the whole chain. (Usually using loop/recur or reduce/reduced, stopping when the result contains an :error key)

what you've made is a useful pattern, and seems idiomatic. Just beware over-generifying functions/over-abstracting

I’m using tools.logging and have a log4j.properties file in src/ which writes logs to a file. However, when I run my tests (with lein test) the logs are still written to stdout (and interleaved with the test output). How do I turn off logging when running my tests?

@ghadi: what do you mean by "I kind of loathe reading code where you have to think about what the parameters, which are functions, take" ?

@oliv: that looks an awful lot like a maybe monad. Take a look: http://clojure.github.io/algo.monads/

@bensu: thank you for your feedback. how would you do ?

@oliv: read this: http://www.clojure.net/2012/02/13/Maybe/

great

I would put the exception handling in m-result to coerce it to nil and then use the same m-bind

but it might be too much for your case

(middleware in general)

yeah, so my functions instead of throw exception would handle inside and returns :error in the container.

ok, let me read your link and try to understand monads

my understanding about monads ( superficial based on my university class in haskell ) is compose computational steps into multi-step computation

right, handling the steps in between with user defined logic.

yeah

you are defining computational steps and you want to stop at any exception, handle it with error-handler and leave

so you can compose your operations with that rule in mind

> you are defining computational steps and you want to stop at any exception, handle it with error-handler and leave exactly

now you can do more interesting things than just (reverse fn-list)

you can compose them however you like and the pattern will still apply.

> now you can do more interesting things than just (reverse fn-list) could you exemplify ? ( if i am not bothering you too much )

well, chain is just one example of composing those functions.

yeah

that suits your syntactic understanding of middleware (which is totally fine)

yeah

if down the road you want to add a conditional between the chaining, where you might have two branches chain doesn't apply anymore

(if auth? auth-middleware-chain non-auth-middlware-chain)

this can be awkward to write using chain (it can, but it won't visually/syntactically reflect your intent)

>if down the road you want to add a conditional between the chaining, where you might have two branches chain doesn't apply anymore yeah, got it

my hunch is that using a monad that captures the rule you mentioned above you can write that code and get your syntax and intent aligned

so, how to handle branching situations

great

let me remember about the monads and I come back later 😄

but I got your point

thanks

sure I'm not an expert either, good luck

thank you, come back later and ping you

hi, a question about the quasiquote. why does args end up as user/args`. But args# ends up as arg__1179__auto__` . I don’t even know what to google for to figure this out.

this is in the context of a macro I was working on.

@shriphani: google for gensym

ah so # is gensym ?

and differs from ’` in behavior? This is quite unexpected (I’ve written macros in racket before).

@shriphani: as you noticed, the back-tick will namespacify your symbol - that won’t happen with apostrophe

yeah any rationale for this behavior ?

the back-tick ` is syntax-quote. Now you can google it 😛

You'll find useful info under syntax-quote in http://clojure.org/reader. The rationale for it comes the concept of "hygienic macros", and this post explains it very well: https://xivilization.net/~marek/blog/2013/09/17/clojure-and-hygienic-macros/

Extracted from that post: > the problem that Lisp macros usually have, they capture the scope of the point where they were called (think dynamic scoping), not where they were defined (think lexical scoping). Various Lisps have solved this problem in different ways, you can find a lot about this on the internet. Clojure has a somewhat unique solution: syntax-quote does not only quote things, it also adds the namespace to things

hey everyone - what's the state of affairs about Clojure tree-shaking, I recall Rich Hickey or someone else tweeting that some progress has been done but can't find the old link