SEDEL: Safe and Expressive Delegation-Based Programming

SEDEL is a new statically-typed and delegation-based object-oriented programming language that supports dynamic composable traits, disjoint polymorphism, intersection types and a merge construct.

SEDEL is written in the Haskell language.

Build and Run

This project can be built with cabal or stack.

• cabal

cabal sandbox init
cabal install --only-dependencies
cabal build
cabal exec SEDEL-exe

• stack

stack build
stack exec SEDEL-exe

REPL

The REPL prompt is >:

• type :q to quit or input any expression in the source language to check its result
• type :load to load a file

> 2
Typing result
: Double

Evaluation result
=> 2.0

Quick Reference

A program consists of list of declarations, ending with a single expression. Like Haskell, a line comment starts with -- and a comment block is wrapped by {- and -}. Declarations include type (type ...) and term (def/defrec ...) declarations:

program := decl ... decl expr
decl    := def ... | type ... | defrec ...

• Primitive type: Double, Bool, String
• Top type/value: () : T
• Type annotation: 2 : Double
• Merge: true ,, 3
• Intersection type: Bool & (Double -> Double)
• If: if x == 0 then true else false
• λ term: (\x -> x+1) : Double -> Double
• Λ term: /\ (A * Double) . (\x -> x) : A -> A
• Disjoint (universal) quantification: forall (A*Int) . A -> A
• Term declaration: def id A (x : A) = x
• Type declaration: type Person = {name : String, male : Bool}

Examples and Case Study

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

stack test