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Clojure

  • It's a lisp (list processor) language
  • Code is made up of lists
  • Every thing in clojure returns a value, therefore lists can be chained
  • Clojure
  • Clojure separates data from functionality
  • Clojure visualizes data
  • Clojure code is data
  • Clojure collections are immutable
  • Clojure is data-oriented
  • Functional Programming
  • Processes input and produce output
  • No change of state at any way!
  • Data structures are immutable, if a change is required, it must be copied with the desired modifications (copy on modification)
  • Immutable by default
  • Value Semantics
  • Thread Safety
  • Null (nil) safety
  • Clojure is compiled language and runs on JVM
  • ClojureScript is interpreted and runs Javascript VM\
# Installation
pacman -S clojure
pacman -S leiningen
paru "babashka-bin" # clojure interpreter

Form

  • A form (aka S-expression - sexp) can be:

  • A symbol

  • A literal

  • Anything enclosed in brackets of some type (), [], {}, ""

  • Special form

  • Special forms compose the base minimum of the clojure language

  • They behave very similar to functions

Symbols

  • Symbols hold values, functions or any other thing
  • A binding is created when a symbol is associated with a thing
  • Symbols are immutable! That's why they are not called variable

Functions

  • Arity: number of parameters that a function receives
  • Higher Order Function: functions that take functions as arguments
  • Predicate: functions that return true/false (usually end with ?)
  • Pure Function
  • Always return the same value for the same input
  • Does not effect anything in its environment (e.g., printing, hitting mutating APIs)
  • Pure functions in clojure usually are not named with verbs but with what it returns

REPL

  • Read Execute/Evaluate Print Loop: quickly test scripts
  • Connects to the running app
  • Modify the app as it is running
  • Jack in
  • It's the start of REPL along with all the necessary dependencies
  • It has built-in configuration for Leiningen, deps.edn and shadow-cljs projects
  • For projects, it must have a project file in the directory open. E.g., project.clj (for leiningen), deps.edn (for deps.edn)
  • CLJD REPL types: Figwheel Main, Lein-Figwheel (legacy figwheel), shadow-cljs
  • nREPL protocol
  • It's used to allow the editor plugin (nREP client) to connect to the Clojure process (nREPL server)
  • It accepts connections and allows the initiation of a program-to-program dialogue
  • It's an asynchronous message-based network protocol for driving interactive development
  • More operations can be supported, or existing operations can be modified or augmented, through nREPL middleware (e.g., piggieback)

Clojure on vscode

  • Calva extension

  • REPL

  • Ctrl Alt C + Ctrl Alt J: start REPL and connect to REPL (project)

  • Ctrl Alt C + Ctrl Alt C: connect to REPL (project)

  • Ctrl Alt O + O: show REPL output window

  • Debug

  • Ctrl Alt C + I: instrument a function to be debugged (you must run the function in REPL afterwards)

  • Evaluation

  • Ctrl Enter: evaluate the current form

  • Alt Enter: evaluate the current top level form

  • Ctrl Alt Enter: evaluate the current enclosing form til cursor

  • Shift Alt Enter: evaluate the current top level form til the cursor

  • Ctrl Alt C + Enter: load current file into REPL

  • Ctrl Alt C + D: interrupt running evaluations

  • Paredit

  • Shift + Alt + Right/Left: expand/shrink sexp selection

  • Ctrl + Right/Left/Down/Up: navigate throughout sexp (forward/backward/down/up)

  • Ctrl + Shift + Right/Left/Down/Up: select throughout sexp (forward/backward/down/up)

  • Ctrl + Alt + Backspace: remove sexp backwards

  • Ctrl + Alt + .: Slurp Sexp Forwards (pull the next Sexp into this Sexp)

  • Ctrl + Alt + ,: Barf Sexp Forwards (push the last Sexp out of this Sexp)

  • Ctrl + Alt + P + R: replace the enclosing Sexp with the current Sexp

  • Formatting

  • Ctrl Alt L: format the code

  • Testing

  • Ctrl Alt C, Shift T: run all tests in the project
  • Ctrl Alt C, T: run tests for current namespace
  • Ctrl Alt C, Ctrl Alt T: run current test

Clojure on intellij

  • Cursive plugin

  • Paredit

  • Ctrl + Shift + I: Slurp Forward (pull the next form into this form)

  • Ctrl + Shift + K: Barf Forward (push the last form out of this form)

  • REPL

  • Ctrl + Shift + R: run REPL

  • Ctrl + Shift + L: reload REPL

  • Ctrl + Shift + P: run top level form

  • Formatting

  • Ctrl + Alt + L: format the code