Simplify inline Clojure code

[daveyarwood]

Closes #108

[crisptrutski]

After all my hard work simplifying things 😉

[daveyarwood]

Sorry @crisptrutski! :)

[daveyarwood]

Quoth @crisptrutski in #89:

The "try alda.lisp namespace first, then fallback to current namespace" has some issues, to furnish an example:

(test-parse :clj-expr "(let [tempo 1] (+ 1 tempo))")
=> (clojure.core/let [alda.lisp/tempo 1] (clojure.core/+ 1 alda.lisp/tempo))

So perhaps a better approach would be to set up a "clean room" namespace, with the appropriate alda.lisp functions referenced, and the conflicting clojure.core functions as exclusions.

We should probably fix this before merging this PR -- seems like it could lead to unexpected behavior :/

[daveyarwood]

Hmm... this is a tricky problem. The Clojure reader must be able to differentiate somehow between symbols in bindings (and their subsequent references) and symbols elsewhere, so that it doesn't try to resolve them, but I haven't figured out how.

[daveyarwood]

@crisptrutski Check this out -- I talked to @micha, and it turns out that all we really need to do to get this working is to refer alda.lisp into the boot.user context. This leverages the way that Boot creates a script at run-time and then evaluates it (you can see the script by running boot -b) in the boot.user namespace.

I've added (require '[alda.lisp :refer :all]) to both the alda script and the build.boot, so that this will work both when running the script and the boot alda task.

This will get trickier in 1.0.0 when we're packaging Alda as an uberjar, and thus won't have access to boot.user, but I think this will do for now.

[crisptrutski]

Looks great, this is exactly what I was thinking also 👍

[daveyarwood]

Brandon Bloom (creator of backtick) had this to say:

Backtick is an implementation of syntax-quote, which operates at the reader level. While Clojure's syntax-quote does leverage knowledge of the dynamic environment (namespaces, vars, etc), it does not have any notion of lexical scope or any high-level understanding of Clojure forms. When your templating code, the normal advice for writing macros applies: Use gensyms:

`(let [tempo# 1] (+ 1 tempo#))

But really, you probably don't want syntax-quote or backtick at all for this use case. Instead, use the normal reader, wrap with `#(list 'fn [] %) and use a combination of in-ns/use/eval.

That last idea -- wrapping the expressions in an anonymous function and using in-ns and/or use in combination with eval -- is worth a try.

[crisptrutski]

Reminds me a bit of JavaScript 😉