As previously demonstrated, it is possible to start up the LFE 'read-eval-print loop' (REPL) using
$ rebar3 lfe repl
Once you are at the LFE prompt, you may write a simple LFE "program" like the following:
lfe> (io:format "~p~n" (list "Hello, World!"))
Or, for the terminally lazy:
lfe> (io:format "~p~n" '("Hello, World!"))
While technically a program, it is not a very interesting one: we didn't create a function of our own, nor did we run it from outside the LFE interactive programming environment.
Let's address one of those points right now. Try this:
lfe> (defun hello-world () lfe> (io:format "~p~n" '("Hello, World!")))
This is a simple function definition in LFE.
We can run it by calling it:
lfe> (hello-world) ;; "Hello, World!" ;; ok
When we execute our
hello-world function, it prints our message to
standard-output and then lets us know everything really quite fine with a friendly
ok. LFE displays
ok as output for functions that do not return a value.
Now let's address the other point: running a Hello-World programming from outside LFE.
<CTRL-G><Q> to exit the REPL and get back to your terminal.