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@cgrand
cgrand / packed-printer.clj
Created Nov 22, 2017
Experiment in compact pretty printing
View packed-printer.clj
=> (doseq [w (range 32)]
(prn 'width w)
(render (best-layout (spans '(1 2 3 4 (a b c) 5 6)) w))
(newline))
width 0
width 1
width 2
@cgrand
cgrand / join.clj
Created Oct 14, 2017
Join transducer
View join.clj
(defn join
"Joins pairs returned by nested transducers based on their key (first item).
Each nested transducer must returns pairs made of a strictly increasing key and a value.
Emits pairs made of the join key and a vector of the joined values (nil when none).
Values in the vector appears in the same order as the xform that produced them."
([] identity)
([xform] xform)
([xform1 xform2]
(fn [rf]
(let [vq1 (volatile! clojure.lang.PersistentQueue/EMPTY)
View de-bruijn.clj
; ported from https://en.wikipedia.org/wiki/De_Bruijn_sequence#Algorithm
(defn- de-bruijn "generate de-bruijn sequences of size n and with elements in 0..k (k excluded)." [k n]
(let [a (into [] (repeat (* k n) 0))
db (fn db [a t p]
(if (> t n)
(into a (when (zero? (mod n p)) (subvec a 1 (inc p))))
(let [a (assoc a t (nth a (- t p)))
a (db a (inc t) p)]
(reduce
(fn [a j]
View foami.clj
(ns foami.core
"FOreign Asynchronous Mechanism Interop"
(:require [clojure.core.async :as async]))
(defn put!
"Takes a `ch`, a `msg`, a single arg function that when passed `true` enables backpressure
and when passed `false` disables it, and a no-arg function which, when invoked, closes the
upstream source."
[ch msg backpressure! close!]
(let [status (atom :sending]
@cgrand
cgrand / doc.clj
Created Sep 14, 2017
Documenting specs inline
View doc.clj
(defmacro doc
"Returns a spec which acts in all points like the provided spec,
expect for describe/form where the docstring appears."
[docstring spec]
`(doc-impl ~docstring '~spec (delay (spec/spec ~spec))))
(defn doc-impl [docstring form delayed-spec]
(reify spec/Spec
(conform* [_ x] (spec/conform* @delayed-spec x))
(unform* [_ y] (spec/unform* @delayed-spec y))
@cgrand
cgrand / scope.md
Last active Sep 6, 2017
Introspectable js scope
View scope.md
// assuming b is a local
// rewrite
function(a) { return a + b; }
// to
Object.defineProperty(function(a) { return a + b; }, "$scope", {value: function() { return {"b": b}; }})
@cgrand
cgrand / bp.clj
Created Sep 1, 2017
pseudo code for back pressure bridging
View bp.clj
(a/go-loop [async-tcp-connections-to-chans ; "foreign" -> ch
buffered ; ch -> data
pressurized] ; ch -> foreign
(let [cnx (select (keys async-tcp-connections-to-chans))
ch (async-tcp-connections-to-chans cnx)
data (read-data cnx)
async-tcp-connections-to-chans (dissoc async-tcp-connections-to-chans cnx)
buffered (assoc buffered ch data)
pressurized (assoc pressurized ch cnx)]
View trace.clj
;; it's very rough (no line info displayed yet, no return value, no filter etc.)
;; but I believe this is the most comprehensive tracing for Clojure
user=> (trace #(reduce + (range 5)))
> user$eval144$fn__145 / invoke
> clojure.lang.Var / getRawRoot
< clojure.lang.Var / getRawRoot
> clojure.lang.Var / getRawRoot
< clojure.lang.Var / getRawRoot
> clojure.lang.Var / getRawRoot
@cgrand
cgrand / kein.sh
Last active May 31, 2017
Launch a plain clojure repl according to project.clj without leiningen (most of the time)
View kein.sh
#!/bin/bash
# launch a clojure plain repl but with options and classpath matching project.clj
# Except when project.clj changes (and on first launch), lein is not called.
CODE='
(let [p (leiningen.core.project/read)
args (@(var leiningen.core.eval/get-jvm-args) p)
cp (with-out-str (leiningen.classpath/classpath p))]
(print "ARGS=\"")
(apply print args)
View reader and spaces.md

While writing a new reader I used clojure.lang.LispReader code as the reference and I discovered there are two type of spaces:

  • pure whitespace (anything that matches #"[ \t\n\r,]+"),
  • unvalued stuff (any sequence of: whitespace, comments, discard (#_), elided conditionals).

This leads to some quirks. For example in namespaced map syntax is:

namespaced-map:
  "#:" (?! whitespace) unvalued-stuff symbol whitespace map
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