Function definition: Difference between revisions

Langur functions are first-order. They are pure in terms of setting values and in terms of I/O (unless declared impure).

A return statement may be used, but a function's last value is its implicit return value.

=== parameters ===

Parameters are defined within parentheses after the fn token. To specify no parameters, use an empty set of parentheses.

<syntaxhighlight lang="langur">val multiply = fn(x, y) { x * y }

multiply(3, 4)</syntaxhighlight>

=== operator implied functions ===

Operator implied functions are built using an infix operator between curly braces on an fn token.

<syntaxhighlight lang="langur">val multiply = fn{*}

multiply(3, 4)</syntaxhighlight>

=== nil left partially implied functions ===

These are built with an infix operator and a right-hand operand inside the fn{ } tokens.

<syntaxhighlight lang="langur">val times3 = fn{* 3}

map times3, [1, 2, 3]</syntaxhighlight>

=== impure effects ===

Functions with impure effects must be declared as such, using fn*.

val writeit = fn*(x) { writeln x }

Impure functions cannot be passed to pure functions.