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Chaining promises

Chaining promises in ClojureScript is best done using the thread-first macro, ->. Here's an example of using the fetch API:

(-> (js/fetch "/data")
    (.then (fn [r]
             (when-not (.-ok r)
               (throw (js/Error. "Could not fetch /data")))
             (.json r)))

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Setting up shadow-cljs cljs REPL in Cursive

See

• https://shadow-cljs.github.io/docs/UsersGuide.html#_cursive
• https://andrearichiardi.com/blog/posts/clojurescript-cursive-shadow-setup.html

1. in shadow-cljs.edn:

 ,,,

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;;
;; Take a textfile which contains a copy of the raw html of a humblebundle user account download
;; select the download page html table with the mouse copy+paste in a textfile
;; Use this file to create a list of folders based on the download names.
;;
;; === TEXT FILE CONTENT EXAMPLE ===
;; Book of Making – Volume 1
;; Raspberry Pi Press
;; PDF
;; 49 MB md5

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  87 luminus: a template for creating Luminus applications
   7 mala: A Leiningen template for Mala
   1 maple: A leinginen template with MPL
   3 mesos-framework: A template for setting up mesos-frameworks using component.
   3 mies-brepl: A minimal ClojureScript project template with REPL
   7 mies-node: A minimal ClojureScript Node.js project template
  27 mies-om: A minimal Om project template
   2 mies-weasel: A minimal ClojureScript project template with Weasel REPL, forked from mies.
  40 mies: A minimal ClojureScript project template
   3 mies: FIXME: write description

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      1 acorn: A Leiningen template for a ClojureScript setup with Figwheel, Austin, Om.
      8 amp: Leiningen template for AMP (Alfresco Module Package) projects.
      1 angular-cl2: A Leiningen template for using AngularJS and ChlorineJS
      1 angular: Clojure and AngularJS in perfect harmony.
      6 angular: Clojure and AngularJS in perfect harmony. $ lein new angular <name>
      2 angularjs-app: Leiningen template for web application with http-kit and angularjs
      5 angular-simple: Clojure and AngularJS $ lein new angular-simple <name>
      1 aperiodic-cljs: My cljs development starting point. Basically ripped from lein-cljsbuild.
      1 apijr: clojurescript project template
      1 appfgo: 'lein new' template for Funcgo application

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Clojure Destructuring Tutorial and Cheat Sheet

(Related blog post)

Simply put, destructuring in Clojure is a way extract values from a datastructure and bind them to symbols, without having to explicitly traverse the datstructure. It allows for elegant and concise Clojure code.

Vectors and Sequences

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@echo off

setLocal EnableExtensions EnableDelayedExpansion

set LEIN_VERSION=2.9.1

if "%LEIN_VERSION:~-9%" == "-SNAPSHOT" (
    set SNAPSHOT=YES
) else (
    set SNAPSHOT=NO

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module Dapper.Extensions

open System
open System.Data.SqlClient
open Dapper

let extractValue (x:obj) =
   match x with
   | null -> null
   | _ -> match x.GetType().GetProperty("Value") with

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// General hints on defining types with constraints or invariants
// 
// Just as in C#, use a private constructor 
// and expose "factory" methods that enforce the constraints
//
// In F#, only classes can have private constructors with public members. 
//
// If you want to use the record and DU types, the whole type becomes
// private, which means that you also need to provide:
// * a constructor function ("create").

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Convention: Byte array notation as it would appear in a hexeditor.

= Layout=

KDBX files, the keepass database files, are layout as follows:

1) Bytes 0-3: Primary identifier, common across all kdbx versions: 
  private static $sigByte1=[0x03,0xD9,0xA2,0x9A];

2) Bytes 4-7: Secondary identifier. Byte 4 can be used to identify the file version (0x67 is latest, 0x66 is the KeePass 2 pre-release format and 0x55 is KeePass 1)