Flix (programming language): Difference between revisions

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=== Higher-Order Functions ===

The following program fragment defines a function <code>twice</code> that when given a function <code>f</code> returns a new function that applies <code>f</code> two times to its argument:

<syntaxhighlight lang="Scala">

/// Returns the sum of x and y.

def add(x: Int, y: Int): Int = x + y

<syntaxhighlight lang="Scala">

/// Returns x plus one.

def inc(x: Int): Int = add(x, 1)

/// Returns a function that applies f twice.

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

</syntaxhighlight>

The <code>twice</code> function can be used as follows:

/// Returns x plus two.

def two(x: Int): Int = twice(inc)(x)

<syntaxhighlight lang="Scala">

def addinc(x: Int, y: Int): Int = x + y1

def inctwo(x: Int): Int = addtwice(x, 1inc)(0)

/// Returns 123 plus 4 = 127.

def main(): Int = twice(two)(123)

</syntaxhighlight>