Flix (programming language): Difference between revisions

Revision as of 07:26, 29 December 2020

Revision as of 08:42, 30 December 2020

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The following program prints "[["Hello, World!" program|Hello World!]]" when compiled and executed:

<syntaxhighlight lang="scalaflx">

def main(): Unit & Impure =

Console.printLine("Hello World!")

Line 62:

The following program fragment declares an [[algebraic data type]] (ADT) named <code>Shape</code>:

<syntaxhighlight lang="scalaflx">

enum Shape {

case Circle(Int), // has circle radius

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The following program fragment uses [[pattern matching]] to destruct a <code>Shape</code> value:

<syntaxhighlight lang="scalaflx">

def area(s: Shape): Int = match s {

case Circle(r) => 3 * (r * r)

Line 86:

The following program fragment defines a [[higher-order function]] named <code>twice</code> that when given a function <code>f</code> from <code>Int</code> to <code>Int</code> returns a function that applies <code>f</code> to its input two times:

<syntaxhighlight lang="scalaflx">

def twice(f: Int -> Int): Int -> Int = x -> f(f(x))

</syntaxhighlight>

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We can use the function <code>twice</code> as follows:

<syntaxhighlight lang="scalaflx">

twice(x -> x + 1)(0)

</syntaxhighlight>

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The following program fragment illustrates a [[Parametric polymorphism|polymorphic function]] that maps a function <code>f: a -> b</code> over a list of elements of type <code>a</code> returning a list of elements of type <code>b</code>:

<syntaxhighlight lang="scalaflx">

def map(f: a -> b, l: List[a]): List[b] = match l {

case Nil => Nil

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The following program fragment shows how to construct a [[Record (computer science)|record]] with two fields <code>x</code> and <code>y</code>:

<syntaxhighlight lang="scalaflx">

def point2d(): {x: Int, y: Int} = {x = 1, y = 2}

</syntaxhighlight>

Line 123:

Flix uses [[row polymorphism]] to type records. The <code>sum</code> function below takes a record that has <code>x</code> and <code>y</code> fields (and possibly other fields) and returns the sum of the two fields:

<syntaxhighlight lang="scalaflx">

def sum(r: {x: Int, y: Int | rest}): Int = r.x + r.y

</syntaxhighlight>

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The following are all valid calls to the <code>sum</code> function:

<syntaxhighlight lang="scalaflx">

sum({x = 1, y = 2})

sum({y = 2, x = 1})