this_is_fun.erl

-module(this_is_fun).

-export([have_fun/0]).
-export([loop/0]).

have_fun() ->
    table = ets:new(table, [named_table]),
    F = fun(X) -> X + 1 end,
    ets:insert(table, {function, F}),
    register(funny, spawn(?MODULE, loop, [])).

loop() ->
    receive
        X ->
            [{function, F}] = ets:lookup(table, function),
            io:format("~p", [F(X)])
    end,
    loop().

1> c(this_is_fun).
{ok,this_is_fun}
2> this_is_fun:have_fun().
true
3> funny ! 10.
1110
4> l(this_is_fun).        
{module,this_is_fun}
5> funny ! 10.    
1110
6> l(this_is_fun).
{module,this_is_fun}
7> funny ! 10.    
** exception error: bad argument
     in operator  !/2
        called as funny ! 10

Have the students explain why:

• The crash happens
• The reason behind 1110 being printed out.