Declarative Programming

Related: Functional Oriented Programming, React-style programming

What is Declarative Programming?

A program that describes what computation should be performed, not how to compute it.

Facebook's React and Imikimi's ArtReact are examples of declarative style programming.

DSL (Domain Specific Languages)

Declarative programming in an imperative language like JavaScript typically takes the form of embedded DSLs. CaffeineEight is a DSL for writing parsers. Below is an example of a complete Json parser using CaffeineEight, written in CaffeineScript.

class JsonParser extends &CaffeineEight.Parser

  @rule
    root: :array :object

    array:
      "" '[' _? ']'
      "" '[' _? value commaValue* _? ']'

    object:
      "" '{' _? '}'
      "" '{' _? pair commaPair* _? '}'

    commaValue: "" _? ',' _? value
    commaPair:  "" _? ',' _? pair
    pair:       "" string _? ':' _? value

    value: :object :array :number :string :true :false :null

    string: /"(?:[^"\\]|\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4}))*"/
    number: /-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?/
    true:   /true/
    false:  /false/
    null:   /null/
    _:      /\ +/

CaffeineScript Enhancements for Declarative Programming

• Class Definition which allows method invocation as well as declaration
• Blocks Instead of Brackets
• Expressive Literals