Emacs CIDER

Introduction#

CIDER is the acronym for Clojure(script) Interactive Development Environment that Rocks. It is an extension to emacs. CIDER aims to provide an interactive development environment to the programmer. CIDER is built on top of nREPL, a networked REPL server and SLIME served as the principle inspiration for CIDER.

Function Evaluation

CIDER function cider-eval-last-sexp can be used to execute the the code while editing the code inside the buffer. This function is by default binded to C-x C-e or C-x C-e.

CIDER manual says C-x C-e or C-c C-e will:

Evaluate the form preceding point and display the result in the echo area and/or in an buffer overlay.

For example:

(defn say-hello
  [username]
  (format "Hello, my name is %s" username))

(defn introducing-bob
  []
  (say-hello "Bob")) => "Hello, my name is Bob"

Performing C-x C-e or C-c C-e while your cursor is just ahead of the ending paren of say-hello function call will output the string Hello, my name is Bob.

Pretty Print

CIDER function cider-insert-last-sexp-in-repl can be used to execute the the code while editing the code inside the buffer and get the output pretty printed in a different buffer. This function is by default binded to C-c C-p.

CIDER manual says C-c C-p will

Evaluate the form preceding point and pretty-print the result in a popup buffer.

For example

(def databases {:database1  {:password "password"
                             :database "test"
                             :port "5432"
                             :host "localhost"
                             :user "username"}
                  
                :database2 {:password "password"
                            :database "different_test_db"
                            :port "5432"
                            :host "localhost"
                            :user "vader"}})

(defn get-database-config
  []
  databases)

(get-database-config)

Performing C-c C-p while your cursor is just ahead of the ending paren of get-database-config function call will output the pretty printed map in a new popup buffer.

{:database1
 {:password "password",
  :database "test",
  :port "5432",
  :host "localhost",
  :user "username"},
 :database2
 {:password "password",
  :database "different_test_db",
  :port "5432",
  :host "localhost",
  :user "vader"}}