Power Tools: Anonymous Functions, Enum & the Pipe Operator

Enemy 1 of 5

Anonymous functions

Sometimes you need a small function just for one specific call site — passing a "rule" to another function — and defining a whole named module function for it would be overkill. An anonymous function is written `fn params -> body end` and, unlike a named function, is called with an explicit dot before the parentheses: `square.(6)`. That dot is a real syntactic requirement in Elixir, not a stylistic choice — it's what tells the compiler "call the function value bound to this name," as opposed to a named function call.

Anonymous functions are ordinary values: you can bind one to a variable, pass it as an argument, or return it from another function, exactly like a number or a string.