A pid file should be reliable

Many Linux/Unix variants have mktemp commands with guarantees of safety if many processes are trying to do so at once. I wouldn't be surprised if there are other related system calls and/or even utility commands that apply for creating and removing lock files.

Why doesn’t this Java interop work?

(String/format "Hello, %s!" "Larry")

Execution error (ClassCastException) at bg-clj.core/eval2010 (form-init14869047494885852816.clj:1).
class java.lang.String cannot be cast to class [Ljava.lang.Object; (java.lang.String and [Ljava.lang.Object; are in module java.base of loader 'bootstrap')

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#format(java.lang.String,%20java.lang.Object...)

String#format takes a String and and array of Object

The Classname... syntax in Java means “varargs”, but it actually unpacks to an array in the compiler. So Object...means “Object array”

@aryyya.xyz ^

So if you want to use String#format, you must do something like: (String/format "Hello, %s!" (object-array ["Larry"]))

OR (and this is the preferred route), use clojure.core/format (https://clojuredocs.org/clojure.core/format)

which does the exact same for you

@potetm Ah ok, thanks for the explanation! I’m trying to do a bit of interop right now just learn how to do it properly. I’d use the Clojure format function otherwise.

What are the best options for parsing BNFs?

there's something right up your alley: https://github.com/Engelberg/instaparse

(:name person) and (person :name) where person is a map seem to do the same thing. Is one preferable over the other stylistically? They both seem a little bit magic over using (get person :name).

not magic they just implement IFn. Also extremely common. There is a difference: a literal won't be null, the person binding might be. A null in the first position will throw whereas a lookup in null will return null

contrast (:a nil) versus (nil :a) in your repl.

generally I don't see maps used as functions unless it's being leveraged in a higher-order function, like (map person list-of-keys-i-want-to-lookup).