Erlang runtime error - erlang

Question

I'm working on an erlang program and getting a strange runtime error. Any idea why? Thanks!
The errors are (after compiling the program successfully):
8> PID = spawn(planner,start,[]).
** exception error: no match of right hand side value <0.65.0>
9>
This is the program:
-module(planner).
-export([start/0]).
start() ->
loop([],[]).
loop(ContactsList,EventsList) ->
receive
{contact, Last, First, Number} ->
loop([{Last,First,Number}|ContactsList],EventsList);
{event, Date, Time, What} ->
loop([{Date,Time,What}|ContactsList],EventsList);
print_contacts ->
NewList=lists:sort(ContactsList),
lists:foreach(fun(Elem)->io:format("~p~n", [Elem]) end, NewList),
loop(ContactsList,EventsList);
print_events ->
NewList=lists:sort(EventsList),
lists:foreach(fun(Elem)->io:format("~p~n", [Elem]) end, NewList),
loop(ContactsList,EventsList);
exit ->
io:format("Exiting.~n");
_ ->
io:format("Dude, I don't even know what you're talking about.~n"),
loop(ContactsList,EventsList)
end.

Answer 1

The variable PID is probably set to something else but <0.65.0> from an earlier line you entered in the shell:
5> PID = spawn(...).
<0.42.0>
8> PID = spawn(...).
** exception error: no match of right hand side value <0.65.0>
This effectively makes the line which generates the error something like
8> <0.42.0> = <0.65.0>.
which will result in a "no match" error.
More obvious illustration of the issue:
1> X = 1.
1
2> X = 2.
** exception error: no match of right hand side value 2
As to solving your issue: You probably want to run f(PID) to have the shell forget just the PID variable, or even f() to have the shell forget ALL variables.