reconstructorepl

An in-progress experiment in making it trivial to move a complete, minimal tree of interdependent expressions from the REPL to a source file.

Quick start v1

[21:14]reconstructorepl> lein repl

user=> (require '[reconstructorepl.core :as rc])
nil
user=> (rc/saving-repl)
***> (def a 1) ; Now we're in an inner repl that stores defining forms
#'user/a
***> (def b 2)
#'user/b
***> (def c 3)
#'user/c
***> (def d (+ a b))
#'user/d
***> (defn f [x] (* x d)**
#'user/f
****> ;; build-defs prints a complete, minimal, ordered sequence of definitions which can be copy/pasted into your source file.
***> (rc/build-defs 'c) ; `c` stands alone; no other defs are needed.
((def c 3))
***> (rc/build-defs 'f) ; whereas `f` depends on `a`, `b`, and `d`.
((def b 2) (def a 1) (def d (+ a b)) (defn f [x] (* x d)))
***> q ; `ctrl-d` or `q` to exit
user=> (f 4) ; vars we defined are still available after we exit the inner repl
12
user=> (rc/build-defs 'd) ; and `build-defs` still works fine
((def b 2) (def a 1) (def d (+ a b)))

Quick start v2

If you don't want to use a special inner repl, just replace def and defn in your ordinary repl with reconstructorepl.redef/def' and reconstructorepl.redef/defn', and you can call reconstructorepl.core/build-defs as above:

[21:14]reconstructorepl> lein repl

user> (require '[reconstructorepl.core :as rc])
nil
user> ;; Note that the order you require these nss in is (currently, and unfortunately) important
user> (require '[reconstructorepl.redef :as rr :refer [def' defn']])
nil
user> (def' a 1)
#'user/a
user> (def' b (inc a))
#'user/b
user> (def' c (+ a b))
#'user/c
user> (defn' f [t] (* t (inc c)))
#'user/f
user> ;; build-defs prints a complete, minimal, ordered sequence of definitions
user> ;; which can be copy/pasted into your source file.
user> ;; `b` depends on `a`
user> (rc/build-defs 'b)
((def a 1) (def b (inc a)))
user> ;; whereas `f` depends on `a`, `b`, and `c`
user> (rc/build-defs 'f)
((def a 1) (def b (inc a)) (def c (+ a b)) (defn f [t] (* t (inc c))))

Rationale

I do a lot of my coding in the REPL. Often after an extended session, in which I've tried various approaches to a problem, including various missteps, I've found a solution I like. Then I have to go back through my REPL history and try to pick out only the complete, minimal sequence of expressions that compose my solution. I may have redefined the same var multiple times as I refined my understanding, and have to be sure to pick out only the correct version. Often I've cleared the buffer, which means I can't jump to the definition. It's always doable -- but after a long REPL session, it can be tedious and error-prone.

Reconstruct-o-REPL is an experiment in making that process trivially easy.

The approach can vary on (at least) two axes. First, there are two strategies I've come up with for causing defining forms to be stored: working in a custom REPL or using a custom variant of def/defn. Second, there are two places where the extra info to be stored: in a central registry or in var metadata. See above for details on how to use each strategy. As it happens, I've written it so that the custom repl uses a registry, and the the special def' and defn' use var metadata, but you could swap those and everything would work fine -- the two axes are completely independent.

Here are the two strategies I've implemented so far:

0. For both strategies, start in an ordinary REPL.

1. A REPL with a custom :read function (reconstructorepl.core), which stores the form in a registry. You can start the custom REPL via (saving-repl). While (or after) using it, calling (build-defs 'a) (for some var a defined in the custom REPL) will print a complete, minimal, ordered sequence of statements which can be copy/pasted into your source file.

2. Custom def and defn, storing the form in the var metadata: within the ordinary REPL, just call reconstructorepl.redef/def' and reconstructorepl.redef/defn' in place of ordinary def and defn. At any time, call (build-defs 'a) as before.

NOTE: requiring reconstructorepl.core switches storage to registry; requiring reconstructorepl.redef switches it to metadata. Currently, whichever namespace you've required most recently dictates whether you should use the custom repl or the custom def/defn. This is kind of dumb, and at some point I'll try to get around to approaching it differently, or ideally making either approach work with either storage strategy.

License

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.