Skip to content

Instantly share code, notes, and snippets.

Christophe Grand cgrand

View GitHub Profile
View decay.clj
(ns net.cgrand.decay
"Exponentially decaying lists. See
for background and for documentation")
;; PRNG, formulas straight from java.util.Random javadoc
(defn- seed ^long [^long n]
(bit-and (unchecked-multiply n 0x5DEECE66D)
(unchecked-dec (bit-shift-left 1 48))))
(defn- next-seed ^long [^long seed]
View maze-generation
(require '[clojure.string :as s])
(defn north-of [[row col]] [(dec row) col])
(defn south-of [[row col]] [(inc row) col])
(defn west-of [[row col]] [row (dec col)])
(defn east-of [[row col]] [row (inc col)])
(defn neighbours [rows cols cell]
cgrand / heredoc.clj
Last active Jan 26, 2019
An ugly hacky heredoc for Clojure
View heredoc.clj
(defn heredoc []
(let [delim (.readLine *in*)]
(->> (repeatedly #(.readLine *in*))
(take-while #(not= delim %))
(interpose \newline)
(apply str))))
; The following lines are read (by the reader) as:
; "Look )(\"\\T\na here doc!\n"
cgrand /
Created May 21, 2013
Fork it and paste your TRON bot
cgrand / restrict-map.clj
Created May 29, 2012
Restricting nested maps to keys of interest
View restrict-map.clj
;; I could have used a closed dispatch (aka cond) but you may find this version more enjoyable
;; the spec format is the one provided by BG
(defprotocol Selector
(-select [s m]))
(defn select [m selectors-coll]
(reduce conj {} (map #(-select % m) selectors-coll)))
(extend-protocol Selector

Monotonic logic is eventually consistent. Eventual Consistency ( has clear limits. It doesn't matter while you are pure. It matters when you go impure (FP). So boundaries must be clear. Boundaries implies coordination. Impure snapshots are expensive.

Monotonicity is ~ relativity. Impure is ~ absolute

cgrand / maze.clj
Created Jan 24, 2011
A maze generator (Wilson's algorithm) which can work with any topography (hextiles, torus variants, teapot etc.)
View maze.clj
; output images (square maze)
; (hex maze)
;; generic Wilson's algorithm implementation
(defn maze
"Returns a random maze carved out of walls; walls is a set of
2-item sets #{a b} where a and b are locations.
The returned maze is a set of the remaining walls."
cgrand / core.cljc
Last active May 11, 2018
Mixing macros and code in cljc and supporting clj, cljs and self-hosted cljs, see
View core.cljc
;; SEE:
;; macros and code in a single cljc working across clj, cljs and self-hosted cljs
;; require clojurescript from master
(ns foo.core
#?(:cljs (:require-macros
[net.cgrand.meta-macros :refer [macros no-macros]]
[foo.core :refer [add]])
:clj (:require
cgrand / ednrepl.clj
Last active Mar 28, 2018
What if a REPL out was a stream of EDN forms?
View ednrepl.clj
;; some sample interaction with a clojure socket repl whose output stream consists only of valid edn forms.
;; the edn stream is not meant for the end user but for the client UI.
;; it demoes several features:
;; • prompt, out, err, eval and exceptions are demultiplexed; unstructred ones (err & out) are just text but the others give data.
;; • elided content (because data too deep or wide) is replaced by a tagged literal (which optionally contains the expr to evaluate to get more items)
;; this last point makes possible navigation
;; lines are prefixed by > or < to tell what is sent to the repl (>) and what is received from it (<)
View lambda-sim.clj
(defn lambda-model
"Crude model. rps is requests per second, len is a function that returns the
execution length in seconds, until is the number of seconds to run the simulation,
spawn is a function returning the number of ping sub requests, duty is the max age
for a container, keep-alive is the number of seconds before decommissioning a
Returns a map with: the number of user perceived cold starts and the number of
billable seconds."
[{:keys [rps len until spawn duty keep-alive]
:or {rps 10
You can’t perform that action at this time.