Anonymous Functions
An anonymous function is a tiny nameless helper written on the spot, like a quick note of instructions. It is handy for short jobs such as doubling each number.
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Syntax
val function_name = (param: Type) => expression
val other = (a: Type, b: Type) => expression
collection.map(_ * 2)Anonymous Functions
An anonymous function (or "lambda") is a function value written inline without a name, using (params) => expression syntax, commonly passed directly to a higher-order function like map.
The placeholder underscore _ offers an even more compact shorthand for simple single-argument cases, like _ * 2. Anonymous functions avoid the ceremony of a full named def for short, one-off logic.
Note:
The underscore shorthand, like
numbers.map(_ * 2), is Scala's most concise way to write a simple single-parameter anonymous function.Example: Anonymous Functions
object Main extends App {
val numbers = List(1, 2, 3, 4)
val squared = numbers.map(n => n * n)
val doubled = numbers.map(_ * 2)
println(squared)
println(doubled)
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Related Topics
{# common_mistakes/chapter_summary/browser_support: on Hindi pages the
view already swaps in the hi_ translation fields (or blanks these
out if untranslated), so this renders correctly for both languages
without a lang_code check here. #}
Common Mistakes
- Using
_twice likenumbers.map(_ * _)and expecting one value, when each underscore stands for a different parameter. - Using
_inside a nested expression such asmap(foo(_ + 1)), where it expands to the wrong function. - Writing
n -> n * ninstead ofn => n * n, when->makes a tuple.
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