My first Erlang program. Functional Programming in Erlang course

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) ->
  3 * X.

second.erl

-module(second).
-export([hypotenuse/2, perimeter/2, area/2]).

hypotenuse(A, B) ->
  math:sqrt(first:square(A) + first:square(B)).

perimeter(A, B) ->
  A + B + hypotenuse(A, B).

area(A, B) ->
  A * B / 2.

Excellent! But if you're going to use first:mult/2 to multiply… you should go all the way and use it to multiply by 1/2, too ;)

Excellent! But if you're going to use first:mult/2 to multiply… you should go all the way and use it to multiply by 1/2, too ;)

Yeah, it's weird :) mult function is useless. Fixed