My first Erlang program

first.erl

-module(first).

-export([double/1,mult/2,area/3,square/1,treble/1]).


mult(X,Y) ->

    X*Y.

double(X) ->

    mult(2,X).

area(A,B,C) ->

    S = (A+B+C)/2,
    math:sqrt(S*(S-A)*(S-B)*(S-C)).


square(X) ->

    X*X.


treble(X) ->

    X*X*X.