comnik

{:deps
 {org.clojure/clojure      {:mvn/version "1.9.0"}
  com.datomic/datomic-free {:mvn/version "0.9.5697"}}}

gvolpe

Dependency Injection in Functional Programming

There exist several DI frameworks / libraries in the Scala ecosystem. But the more functional code you write the more you'll realize there's no need to use any of them.

A few of the most claimed benefits are the following:

• Dependency Injection.
• Life cycle management.
• Dependency graph rewriting.

comnik

(defn relate [& pairs]
  (assert (even? (count pairs)) "relate requires an even number of arguments")
  (->> pairs
       (partition 2)
       (map (fn [[k vs]] (map #(hash-map k %) vs)))
       (apply map merge)))


(defn matches-specmap? [specmap m]
  (reduce-kv

borkdude

(ns specter-idea
  (:require [com.rpl.specter :as specter :refer [setval ALL
                                                 NONE multi-path
                                                 selected?
                                                 pred
                                                 ]]))

(def data ;; only x and y are allowed
  [{:name "x" :rels ["x" "y"]} ;=> fine, keep as is
   {:name "y" :rels ["x" "y" "z"]} ;=> keep only allowed rels: {:name "y" :rels ["x" "y"]}

favila

(require '[datomic.api :as d])

(d/create-database "datomic:mem://counter-example")
;=> true
(def c (d/connect "datomic:mem://counter-example"))
;=> #'user/c

;; The essential features of creating and using an auto-increment counter in datomic:
;;
;; 1. A counter entity must store the current value and a nonce.

djspiewak

Thread Pools

Thread pools on the JVM should usually be divided into the following three categories:

1. CPU-bound
2. Blocking IO
3. Non-blocking IO polling

Each of these categories has a different optimal configuration and usage pattern.

reborg

Rich Already Answered That!

A list of commonly asked questions, design decisions, reasons why Clojure is the way it is as they were answered directly by Rich (even when from many years ago, those answers are pretty much valid today!). Feel free to point friends and colleagues here next time they ask (again). Answers are pasted verbatim (I've made small adjustments for readibility, but never changed a sentence) from mailing lists, articles, chats.

How to use:

• The link in the table of content jumps at the copy of the answer on this page.
• The link on the answer itself points back at the original post.

Table of Content

boogie666

(ns logical-db.core
  (:require [clojure.core.logic :as l]
            [clojure.core.logic.protocols :refer [walk]]
            [clojure.core.logic.pldb :as db]))

; [org.clojure/clojure "1.8.0"]
; [org.clojure/core.logic "0.8.10"]


(def db { :city->zip {"City1" [1 2 3 4] "City2" [5 6]}

favila

(def tx-fns
  [{:db/ident :db.fn/reset-attribute-values
    :db/doc "Transaction function which accepts an entity identifier, attribute identifier
 and set of values and expands to any additions and retractions necessary to
 make the final post-transaction value of the attribute match the provided
 values. Attribute values must be scalars.
 
 If multiple values are provided on a cardinality-one attribute you will get a
 datom conflict exception at transaction time."
    :db/fn    (d/function

nathanmarz

(ns specter.zip
  (:use [com.rpl.specter.macros :only [defpath]]
        [com.rpl specter])
  (:require [clojure [zip :as zip]]))

(def VECTOR-ZIP (view zip/vector-zip))
(def NEXT (view zip/next))
(def RIGHT (view zip/right))
(def LEFT (view zip/left))
(def DOWN (view zip/down))