Hello World

Welcome to cljgo by example — a book that teaches you cljgo one small step at a time. Every page starts tiny, grows a little, and ends with something real. Every example is runnable exactly as shown.

No prior Clojure needed.

Say hello

(println "Hello, world!")

Output:

Hello, world!

That’s a complete program. println is a function, and (...) calls it — the function comes first, then its arguments. This one rule is most of the syntax you will ever need.

Print more than one thing

println takes any number of arguments and puts spaces between them:

(println "1 + 2 is" (+ 1 2))

Output:

1 + 2 is 3

Notice (+ 1 2) — even + is just a function called the same way.

Your first function

defn defines a function. This one takes a name and builds a greeting:

(defn greet [who]
  (str "Hello, " who "!"))

(println (greet "cljgo"))

Output:

Hello, cljgo!

str glues values into a string. greet returns it — no return keyword needed, a function always returns its last expression.

Run it

Save any of these as hello.clj:

cljgo run hello.clj    # runs instantly, no build step
cljgo build            # or compile it into one small static binary

Next: the values you’ll be greeting →