The concept of functions in different programming languages

Functions are present in many programming languages. Some of the languages have better support for purely functional styles, while others favor declarative styles. This is why, for example, using Scala over Java can give you tremendous leverage, because you can declare functions inside other functions, you can declare functions that accept other functions (higher-order functions) more easily, and you can declare anonymous lambda functions (functionality also available in Java, starting from Java 8). This greatly increases your capacity for abstraction, creating control structures, and thereby enabling your application to be expressed in a more DRY (Don't Repeat Yourself) way.