(defn signup-user [pgsql new-user] (when (s/validate schemas/User new-user) (sql/save pgsql new-user)))

cool ! and the error messages ?

I would have code that does that

and then I'd have a function higher up, that catches exceptions thrown

and builds the response

in particular, I'd define the exception handler in my routes.clj and this in my controllers.clj (or something similar)

so, my functions must throw an error ?

they don't have to

I find throwing with slingshot is nice

validate and save on your example

in my example, I'd expect validate to throw an exception if the user doesn't pass the schema check, and save to throw an error if the user already exists

interesting approach

(that's also exactly how I'd write my code in python or ruby, fwiw)

exception controlling the flow

in ruby ( active record ) we normally call valid? before the save!

(when (s/validate User new-user) ....) would validate before calling save

it's just the s/validate will return a truthy value (and thus execute the body) if the schema is valid, and it happens to throw an exception if new-user doesn't match that schema

but you can replace s/validate with whatever valid? you'd want to write

Hey, I just created a new chestnut project via lein new chestnut my-project, but after adding datomic I get this error when trying to execute lein repl

Exception in thread "main" java.lang.ExceptionInInitializerError
	at clojure.main.<clinit>(main.java:20)
Caused by: java.lang.IllegalArgumentException: No matching ctor found for class clj_logging_config.log4j.proxy$org.apache.log4j.WriterAppender$ff19274a, compiling:(clj_logging_config/log4j.clj:37:18)

I've been stumped for the past couple of hours, I tried adding the log4j as a dependency, as well as following the directions here http://docs.datomic.com/configuring-logging.html

Came here as a last resort in case anyone had an idea 😄

@haywood I don't know for certain, but that looks like it might be a library version conflict. you might run lein deps :tree and scan for complaints around log4j and/or clj-logging-config

ah, wonderful will try, thank you

looks like possibly clashing with ring.middleware.logger

so in this case I can use exclusion on that package?

you can pin ring.middleware.logger and add an :exclusions [....] to that

Thanks for the pointers @dominicm and @hiredman! Pretty is nice for exceptions but not much beyond that as far as I can tell. I'll also take a look at fipp and that paper. Maybe an interesting project...

Is there some more info then the spec page to learn more about spec

There is the guide http://clojure.org/guides/spec

There are also a number of blogs and screencasts at http://blog.cognitect.com

I'm working on a chapter for the next edition of Programming Clojure but it will be a while before that's available

Are there here people who develop in Linux.if so, which distro do you use ?

@alexmiller thanks. I will read it

That's weird and it does look similar to the referenced bug

You're sure you are using latest Clojure? You can use clojure-version to check

Sorry, stars around that as it's a dynamic variable

If you're reproducing on 1.8 or 1.9, prob should file a ticket in jira for it

I’m new to clojure and I specify the Clojure version in lein’s project.clj

Yeah, checking at the repl can help you verify that it matches what you think it is

Ah, I reproduce it too...

I’m sorry, maybe I confused the versions...

Seems to work the second time though

yes, but I really don’t understand why

@alexmiller can the spec be good for a beginner to use for solving 4clojure puzzles

Seems unlikely

oke, then I will not use it for that. then I wait till I make "real" programms like a web app

counterpoint - i had a fun time using spec to solve http://adventofcode.com/2015 problems - it wasn’t at all necessary to use spec for any of them really, but i found it a useful exercise for getting muscle memory / familiarity with writing+using specs

i was a beginner to spec but not a beginner to clojure, so my experience with advent of code may not be relevant to the discussion

Is there a reasonable way to get all of the possible ways a substring can be replaced by a different substring? I.e. ab -> xy, ababab -> [xyabab, abxyabab, …] (at most one). I’m guessing this is just going to be manual coding + subs

Doesn't sound too complicated

Just gotta think about the edge cases around overlapping matches