Starting Erlang

If you are running on a Unix system type "erl" or, if you are running on Windows start Erlang by clicking on the Erlang start icon. You should see something like this:

os prompt > erl
Erlang R13B (erts-5.7.1) [smp:4:4] [rq:4] [async-threads:0] [kernel-poll:false]

Eshell V5.7.1  (abort with ^G)
1>

The ">" prompt means the system is waiting for input.

Using Erlang as a Calculator

1> 2131836812671*12937192739173917823.
27579983733990928813319999135233
2>

Remember to terminate every expression with a DOT followed by a whitespace!

Editing previous expressions

Previous expressions can be retrieved and edited using simple emacs line editing commands. The most common of these are:

^P

Fetch the previous line.

^N

Fetch the next line.

^A

Go to the beginning of the current line.

^E

Go to the end of the current line.

^D

Delete the character under the cursor.

^F

Go forward by one character.

^B

Go Back by one character.

Return

Evaluate the current command.

Note: ^X means press Control + X. On many systems these control sequences are also mapped to the Arrow (Up,Down,Left,Right) keys.

Try typing Control+P to see what happens.

Compiling your first program

Type the following into a file using your favorite text editor:

-module(test).
-export([fac/1]).

fac(0) -> 1;
fac(N) -> N * fac(N-1).

Store this in a file called test.erl The file name must be the same as the module name. Compile the program by typing c(test) then run it:

3> c(test).
{ok,test}
4> test:fac(20).
2432902008176640000
5> test:fac(40). 
815915283247897734345611269596115894272000000000
6>