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README.md

SAMPL - Sound And Modern Programming Language

Build Status Release GitHub

Note: This project will no longer be maintained. Please take a look at its spiritual successor SAMLANG.

It is a JVM language that embraces the functional programming paradigm, which currently supports immutable data structures, null safety, pattern matching, currying, limited type inference, and limited interop with other JVM languages.

Gradle Config

Add this to your build.gradle to use the artifact.

repositories {
    jcenter()
    maven { url "https://jitpack.io" }
}
dependencies {
    implementation 'com.github.SamChou19815:sampl:+'
}

Scope of this Project

This project aims to implement a type-checker, interpreter, and compiler for this language.

The type-checker will be invoked before both interpretation and compilation to reject all ill-formed code before running. We aim to design a sound type system for this language without any qualification, so this language does not support type cast that can potentially produce type errors at runtime.

The interpreter will not be an REPL. Instead, it only supports the interpretation of an entire program. The compiler will compile the source code of this language to Kotlin code, then invoke the Kotlin compiler to compile it to Java bytecode. This design allows rapid prototyping and lets the generated bytecode have excellent integration with Kotlin codebase.

Notable Features

Type Inference

val a = 42
val b = a + 4
fun main(): Int = a + b

Pattern Matching

class Optional<T>(None | Some of T) {
   fun <T> hasValue(v: Optional<T>): Bool =
     match v with
     | None -> false
     | Some _ -> true
}

Currying

fun add(a: Int, b: Int): Int = a + b
val add1 = add(1)
fun main(): Int = add1(2)

Purely Functional

Since SAMPL is a pure functional language, it can be used to illustrate the concept of "Propositions are types and proofs are programs".

Propositions are SAMPL types

A type parameter in generics info (e.g. A in Or<A, B>) is an atomic proposition.

The Unit type represents TRUE.

// The [And] class below represents logical conjunction.
class And<A, B>(a: A, b: B)
// The [Or] class below represents logical disjunction.
class Or<A, B>(
  First of A | Second of B
)
// This function has type (A) -> B. This is logical implication.
fun <A, B> implication(a: A): B = b

Proofs are SAMPL programs

// This well-typed function is an elegant proof for Modus Ponens.
fun <A, B> modusPonens(f: (A) -> B, v: A): B = f(v)
// This well-typed function is an elegant proof for both A and B are true.
fun <A, B> both(a: A, b: B): And<A, B> = And(a, b)
// This well-typed function is an elegant proof for either A or B implies C.
fun <A, B, C> eitherOneImplies(o: Or<A, B>): C =
  match o with
  | First a -> aToC(a)
  | Second b -> bToC(b)
// This well-typed function shows everything proves true.
fun <A> everythingProvesTrue(a: A): Unit = ()

Getting Started

Pass -interpret [filename] to the jar to interpret the program in filename. Currently, it will prints the result to standard out.

Pass -compile [filename] to the jar to compile the program in filename. Currently, it will prints the equivalent code in Kotlin to standard out.

Documentations

  • Read the language spec for the definition of the language features. Currently, the language is not very precise.

  • Read the design document to understand the overall design and architecture.

Developer Notes

To reduce the size of the package, we do not add the Kotlin compiler as a dependency. If you need a self-contained package, you can easily wrap it. The reason is that people may only need the interpreter features, so the 30M Kotlin compiler is completely useless to them.

This project is still in prototype. There will be no backward-compatible guarantees in the near feature. Especially do not use this in production.

Current Status

  • Version: Alpha 2
  • License: MIT
  • Contributors: ["Sam Zhou"]
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