caiorss

/* Start by creating a reader for some fake yet conceivable type for executing SQL queries. */

val dbReader: Reader[Properties, JdbcExecutor] =
  for {
    driver   <- read[String]("db.driver")
    uri      <- read[String]("db.uri")
    user     <- read[String]("db.username")
    password <- read[String]("db.password")
    name     <- read[String]("db.pool.name")
    minCons  <- read[Int]("db.pool.minConnections")

caiorss

val getJDBCConnection: Reader[JDBCConf, Connection] = ???

val getStatement: Reader[Connection, PreparedStatement] = ???

val executeQuery: Reader[PreparedStatement, ResultSet] = ???

val queryExecutor: Reader[JDBCConf, ResultSet] = getJDBCConnection.andThen(getStatement).andThen(executeQuery)

caiorss

Monad     | effect                                   | sequences the effect as | M[A]         | bind: M[A] => (f: A => M[B]) => M[B]

Identity  | nothing                                  | continue                | Id[A]        | f(a)
Option    | zero or one value (anonymous exception)  | halt if None            | Option[A]    | if Some(a) f(a)
Either    | exception with error type or one value   | halt if Left            | Either[L, A] | if Right(a) f(a)
List      | any # of values (non-determinism)        | halt if empty           | List[A]      | join(each f(a))
Reader    | an environment; dependency-injection     | function composition    | R => A       | (r: R) => f(a(r))
Writer    | logging                                  | append log value W      | Writer[W, A](log: W, value: A) | k = f(a.value); Writer(a.log |+| k.log, k.value)
State     | state                                    | new state from old      | State[S, A](s: S => (S, A))    | 
Responder | continuation-passing

caiorss

/// REPL Testing 
//
// -----------------------------------------

$ scala
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_20).
Type in expressions for evaluation. Or try :help.

scala> case class Reader[C, A](g: C => A) {
     |   def apply(c: C) = g(c)

caiorss

/*
Based on the first part of the talk "Dead-Simple Dependency Injection in Scala" by @runarorama at NEScala 2012
http://marakana.com/s/dependency_injection_in_scala,1108/index.html
*/

class Connection {
  def prepareStatement(query: String) = new Statement()
}

class Statement {

caiorss

(defun postscript-process ()
  (get-buffer-process (get-buffer "*postscript*")))

(defun run-postscript ()
  (interactive)
  (require 'comint)
  (switch-to-buffer (make-comint "postscript" "gs")))
(push '("postscript" . utf-8) process-coding-system-alist)

caiorss

%!PS
%%DocumentMedia: a4 595 842 80 () ()

/pageHeight 842 def
/pageWidth 595 def

<< /PageSize [pageWidth pageHeight] >> setpagedevice

/mm { 2.834645669 mul } def

caiorss

newpath
300.0 400.0 moveto
gsave
currentpoint translate
-241.66666666666669 0.0 rmoveto
108.33333333333334 0.0 rmoveto
gsave
currentpoint translate
-108.33333333333334 0.0 rmoveto
25.0 0.0 rmoveto

caiorss

;; Get package installation ready
(require 'package)
(setq package-enable-at-startup nil)
(add-to-list 'package-archives
             '("melpa" . "https://melpa.org/packages/"))
(package-initialize)

;; Bootstrap `use-package'
(unless (package-installed-p 'use-package)
  (package-refresh-contents)

caiorss

;; 1. place this in ~/.emacs.d/private/intero/packages.el

;; 2. add intero, syntax-checking and auto-completion to your
;; ~/.spacemacs layer configuration & remove the haskell layer
;; if you were using that before

;; 3. make sure you have stack installed http://haskellstack.org

;; 4. fire up emacs & open up a stack project's source files