Flix. Functional. Logical.

Recent News

- 2018-05-01 The paper Tail Call Elimination and Data Representation for Functional Languages on the Java Virtual Machine is now available!
- 2017-10-11 Flix version 0.2 is now available!
- 2017-04-18 Flix version 0.1 is now available!
- 2016-09-25 Ming-Ho Yee's master thesis Implementing a Functional Language for Flix is now available.
- 2016-09-13 The extended abstract Programming a Dataflow Analysis in Flix from TAPAS 2016 is now available.
- 2016-07-14 The poster Flix and its Implementation: A Language for Static Analysis from ECOOP 2016 is now available!
- 2016-07-14 The video from PLDI 2016 is now online!
- 2016-06-20 The slides from the presentation at PLDI 2016 are now available!
- 2016-06-10 The first preview version of Flix is now available!
- 2016-06-10 The paper From Datalog to Flix: A Declarative Language for Fixed Points on Lattices is now available.

At a glance

Flix is a statically typed functional- and logic programming language inspired by Scala, OCaml, F#,
Haskell, and Datalog.
The syntax of Flix resembles Scala and Datalog. The type system supports local type inference and is
based on Hindley-Milner.
Flix runs on the Java Virtual Machine and compiles directly to JVM bytecode.

Flix supports hybrid functional and logic programming featuring a built-in fixed point engine based on
semi-naive evaluation.
The functional and logic languages can be used independently, if so desired.
For example, a Flix program can be purely functional, or Flix can be used as a standalone Datalog
engine.

Fully-featured, batteries included.

#### Functional and Declarative

#### Algebraic Data Types

#### Pattern Matching

#### Namespaces

#### Parallel Rule Evaluation

#### Tail recursion optimization

#### Datalog Support

#### Stratified Negation

#### Standard Library

#### Static Type System

#### Formal Semantics

#### Scala and Prolog-style Syntax

#### Free & Open Source

#### Integrated browser-based Debugger and Profiler

#### Built-in Delta Debugger

#### Built-in QuickChecker

#### Built-in Static Program Verifier

#### Runs on the Java Virtual Machine

#### Tutorials & Documentation

```
VarPointsTo(v, o) :- NewObj(v, o).
VarPointsTo(v1, o) :-
Assign(s, v1, v2),
VarPointsTo(v2, o).
VarPointsTo(v1, o2) :-
Load(v1, v2, f),
VarPointsTo(v2, o1),
HeapPointsTo(o1, f, o2).
HeapPointsTo(o1, f, o2) :-
Store(f, v2),
VarPointsTo(v1, o1),
VarPointsTo(v2, o2).
```

A points-to analysis aims to discover to what object(s) every local variable and field of an object can point-to. The mutually recursive dependencies between local variables and the heap is easy to express in Flix.

```
PathEdge(d1,m,d3) :-
PathEdge(d1,n,d2),
EshIntra(n,d2,d3),
CFG(n,m).
PathEdge(d1,m,d3) :-
PathEdge(d1,n,d2),
SummaryEdge(n,d2,d3),
CFG(n,m).
PathEdge(d3,start,d3) :-
PathEdge(d1,call,d2),
CallGraph(call,target),
EshCallStart(call,d2,target,d3),
StartNode(target,start).
SummaryEdge(call, d4, d5s) :-
CallGraph(call,target),
StartNode(target,start),
EndNode(target,end),
EshCallStart(call,d4,target,d1),
PathEdge(d1,end,d2),
EshEndReturn(target,d2,call,d5s).
```

The IFDS analysis by Reps et al. is a graph reachability problem that can be used to solve certain static analyses. Both IFDS and its extension IDE can be expressed in Flix. Something which is not possible in pure Datalog.

```
enum Parity {
case Top,
case Odd, case Even,
case Bot
}
def leq(e1: Parity, e2: Parity): Bool =
match (e1, e2) with {
case (Bot, _) => true
case (Odd, Odd) => true
case (Even, Even) => true
case (_, Top) => true
case _ => false
}
def lub(e1: Parity, e2: Parity): Parity =
match (e1, e2) with {
case (Bot, x) => x
case (x, Bot) => x
case (Odd, Odd) => Odd
case (Even, Even) => Even
case _ => Top
}
```

A parity analysis aims to discover, for every local variable in a program, whether it is odd or even. We can conveniently express such an analysis as several constraints over a lattice (see above for the lattice definition).

Try Flix in the Online Editor

def f(): Bool = List.exists(x -> x % 42 == 0, List.range(1, 100))

def f(): Int = List.foldLeft((x, y) -> x + y, 0, List.map(x -> x + 1, List.range(1, 10)))

enum Shape { case Circle(Int), case Square(Int), case Rectangle(Int, Int) } def area(s: Shape): Int = match s with { case Circle(r) => 3 * r * r case Square(l) => l * l case Rectangle(l, w) => l * w } def f(): Int = area(Rectangle(10, 20))

rel Edge(x: Int, y: Int) rel Path(x: Int, y: Int) Edge(1, 2). Edge(2, 3). Path(x, y) :- Edge(x, y). Path(x, z) :- Path(x, y), Edge(y, z). def f(): Int = 42

Free, Open Source and Ready to Use.

Flix is open source and available free of charge. The source code for Flix is hosted on GitHub and all development is public.

Flix is dual-licensed under the Apache 2.0 License and the MIT license allowing unrestricted commercial and personal use.

Flix comes packaged as a single JAR-file that runs on any operating system where the Java Runtime Environment is available, including Windows, Linux and Mac OS X. Flix requires Java 1.8.

Sponsors

We kindly thank EJ Technologies for providing us with
JProfiler
and JetBrains for providing us with
IntelliJ IDEA.