# What You Need to Know About Lazy Evaluation in Nix

DevFeed: [What You Need to Know About Lazy Evaluation in Nix](<https://devfeed.tech/articles/what-you-need-to-know-about-lazy-evaluation-in-nix-32454.md>)

Original publisher: [Read original article](<https://nixcademy.com/posts/what-you-need-to-know-about-laziness/>)

Author: Jacek Galowicz

Published: 2024-07-15T00:00:00Z

Content type: tutorial

Language: en

Sources: [Nixcademy Blog](<https://devfeed.tech/sources/nixcademy-blog.md>)

Topics: [Nix](<https://devfeed.tech/topics/nix.md>), [Functional programming](<https://devfeed.tech/topics/functional-programming.md>), [Programming](<https://devfeed.tech/topics/programming.md>)

Tags: [article](<https://devfeed.tech/tags/article.md>), [functional-programming](<https://devfeed.tech/tags/functional-programming.md>), [lazy](<https://devfeed.tech/tags/lazy.md>), [programming](<https://devfeed.tech/tags/programming.md>)

## AI overview

This article explains lazy evaluation in the Nix language, including when expressions are evaluated, how errors can be deferred until a value is referenced, and how thunks model this behavior. It also introduces context for understanding Nix overlays and dependency overrides.

## Source excerpt

If you have no prior experience with functional programming, don't miss this article which explains the most important intricacies of lazy evaluation!