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\"If you wish to make an apple pie from scratch, you must first create the universe.\"
- Carl Sagan, Cosmos

This book is about nothing.

Or, rather, it is about starting with nothing and creating the world. In our day-to-day lives as programmers, we're used to languages that give us a wide range of nouns, concrete structures to work with: Numbers, String, Arrays, and so forth. And we happily combine them, trying to fit them together so that we come out the other end with a large structure that solves our problem.

What we often forget, though, is that, taken by themselves, these structures are useless. When we talk about combining them, we really mean that we set up interactions between them, hoping that we've defined them correctly.

Programming itself is about defining the functions, the interactions BETWEEN the nouns. Yet, we don't spend a lot of time focusing there. Take a look at a UML diagram: notice what gets the big boxes and what gets the small little arrows connecting them.

In Fun With Lambdas, we’re going to start with the most basic function: one that takes a single input and returns a single output. From this, we will build up our world of concrete structures. This basic function has a name, a lambda.

While we are playing with lambdas, we’re going to use some of the fundamental concepts from the lambda calculus, but we stay away from the heavy academic stuff. We give ourselves a bit more freedom to play and see what we can build for fun. Along the way, we'll discuss the nature of booleans; the Peano Axioms for numbers; basic data structures; and, finally end up with a stack-based, functional programming language. We'll then use that language to build some simple turn-based games. And, of course, we’ll do all this test-first, using some testing functions we build ourselves using—what else!—lambdas.

This book is first and foremost intended to be fun. Imagine us sitting down one day, I turn to you and ask \"want to see something cool?\" We open our editor, and then off we go!

Coming July 2020!

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