wxzh / CP

A language for Compositional Programming

Compositional Programming (CP)

This artifact includes the Haskell implementation of the CP language introduced in the TOPLAS paper Compositional Programming. It also contains several examples and three case studies written in CP. All of the CP programs in this artifact can be type-checked and run using our CP interpreter.

⚠️ This repository is not maintained. Please check our new implementation: https://github.com/yzyzsun/CP-next

Docker

The image on Docker Hub can be pulled and run using the following command:

docker run -it yzyzsun/cp

Build from Scratch

This project can be built with Stack.

stack build
stack exec cp-exe

REPL

The REPL prompt is >

• type :q to quit
• type :load to load a file
• type :? for usage

> :load case-studies/mini-interp.cp
Typing result
: String

Evaluation result
=> "letf $f = <Lambda> in let $x = 9.0 in appf $f $x : Double = 81.0"

Quick Reference

A program consists of list of declarations (separated by ;), ended with an expression. Like Haskell, a line comment starts with -- and a comment block is wrapped by {- and -}.

• Primitive type: Double, Int, Bool, String, List
• Top type/value: () : Top
• Bottom type: Bot
• Type annotation: 2 : Int
• Merge: true ,, 3
• Intersection type: Bool & (Int -> Int)
• If: if x == 0 then true else false
• λ term: \(x : Int) -> x + 1
• Λ term: /\ (A * Int) . \(x : A) -> x
• Disjoint quantification: forall (A*Int) . A -> A
• Term declaration: id A (x : A) = x
• Application: id @Int 2
• Type declaration: type Person = { name : String; male : Bool }
• Signature declaration: type Sig<Exp> = { Lit : Int -> Exp; Add : Exp -> Exp -> Exp }
• Trait: trait [self : Person] => { age = 42 }
• Trait type: Trait[Person, Age]
• Method pattern: (Add e1 e2).eval = e1.eval + e2.eval

Examples

See the examples/ directory. All examples can be tested:

stack test

Case Studies

All of the three case studies can be found in the case-studies/ directory:

1. Scans (in CP, Haskell, Scala, and SEDEL): scans.cp, scans.hs, scans.scala, and scans.sl
2. Mini Interpreter: mini-interp.cp
3. C0 Compiler: czero.cp