# Lambda Calculus is Dead! Long live Lambda Calculus!

Introduced by Alonzo Church in the 1930s, $\lambda$-calculus can be considered as the smallest computation programming language of the world. Reading through the various tutorials one can find various examples which showcase its universality; addition, conditional operators, equality and inequality and recursion. One thing which always intrigued me is how applicable is $\lambda$-calculus to everyday problems such as finding the set of URLs in a sitemap or a set of alternate language urls? *The question is obviously rhetorical since we know that $\lambda$-calculus is Turing complete!* Can we model a “modern” problem in terms of $\lambda$-calculus and will such a problem still feel natural? The answer is yes! In this post we are going to apply $\lambda$-calculus in an SEO domain, specifically to construct a Sitemap and to find the hreflang for a language.