Etudes for ClojureScript

Chapter 1. Functions and Variables

This chapter starts with a couple of “warm-up exercises” so that you can get comfortable with your ClojureScript development environment. First, a quick review of how to define functions. Here is the generic model for a function:

(defn function-name [parameters] function-body)

Here is a function that takes an acceleration and an amount of time as its parameters and returns the distance traveled:

(defn distance [accel time] (/ (* accel time time) 2.0)

You can also put a documentation string between the function name and parameter list:

(defn distance
  "Calculate distance traveled by an object moving
  with a given acceleration for a given amount of time."
  [accel time]
  (/ (* accel time time) 2.0)

Étude 1-1: Defining a Function in the REPL

Create a project named formulas (see “Creating a ClojureScript Project”) and start a browser REPL (read/evaluate/print/loop). If you haven’t yet installed ClojureScript, follow the instructions in Appendix B, and create a project to work with. In the REPL, type the preceding distance function and test it.

Étude 1-2: Defining Functions in a Source File

Defining functions in the REPL is fine for a quick test, but it is not something you want to do on an application-level scale. Instead, you want to define the functions in a source file. In the formulas project, open the src/formulas/core.cljs file and create functions for these formulas:

• Distance equals one-half acceleration multplied by time squared:
• Kinetic ...