name-lambda.md

Name Lambda

Relevant To

• Extract Variable

Relates To

• Name Value
• Extract Function

Languages

Languages with lambdas

Motivation

Lambdas/anonymous functions are very useful. However, if is not immediately clear from it is code what one does, it is helpful to give it a name to describe it.

Description

Either store the lambda in a named value or extract it to a new, named function.

Examples

Clojure

Before

(defn tax-multiplier [rate] (+ 1 (/ rate 100)))
(defn with-tax [rate amount] (* amount (tax-multiplier rate)))

(defn order-total
  [items tax-rate]
  (sum (map (fn [item] (with-tax (:amount item))) items))

After

(defn tax-multiplier [rate] (+ 1 (/ rate 100)))
(defn with-tax [rate amount] (* amount (tax-multiplier rate)))

(defn item-amount-with-tax [item] (with-tax (:amount item)))

(defn order-total [tax-rate items] (sum (map item-amount-with-tax items)))