Complete exercise 6.2.

Author: Stratus3D

chapter_6/exercise_2/try_test.erl

@@ -0,0 +1,53 @@
+-module(try_test).
+
+-export([generate_exception/1, demo1/0, demo2/0, demo3/0, polite_and_detailed_messages/0]).
+
+generate_exception(1) -> a;
+generate_exception(2) -> throw(a);
+generate_exception(3) -> exit(a);
+generate_exception(4) -> {'EXIT', a};
+generate_exception(5) -> error(a).
+
+demo1() ->
+    [catcher(I) || I <- [1,2,3,4,5]].
+
+catcher(N) ->
+    try generate_exception(N) of
+        Val -> {N, normal, Val}
+    catch
+        throw:X -> {N, caught, throw, X};
+        exit:X  -> {N, caught, exited, X};
+        error:X -> {N, caught, error, X}
+    end.
+
+demo2() ->
+    [{I, (catch generate_exception(I))} || I <- [1,2,3,4,5]].
+
+demo3() ->
+    try generate_exception(5)
+    catch
+        error:X ->
+            {X, erlang:get_stacktrace()}
+    end.
+
+% Exercise 6.2 says we need to provide two messages for each
+% exception. To do that I duplicated the catcher function above
+% and updated the return value so that is it always two tuples.
+% The first item in the tuple is a tuple representing the polite
+% error message for the user. The second is a tuple of four items
+% for the developer. The last item in the tuple is the stacktrace.
+polite_and_detailed_message(N) ->
+    try generate_exception(N) of
+        Val -> {Val, {N, normal, Val, erlang:get_stacktrace()}}
+    catch
+        throw:X -> {{caught_throw, X}, {N, caught, throw, X, erlang:get_stacktrace()}};
+        exit:X  -> {{caught_exit, X}, {N, caught, exited, X, erlang:get_stacktrace()}};
+        error:X -> {{caught_error, X}, {N, caught, error, X, erlang:get_stacktrace()}}
+    end.
+
+% In order to demonstrate the polite_and_detailed_message
+% function, I created this function called
+% polite_and_detailed_messages. It is almost the same as
+% demo1/0.
+polite_and_detailed_messages() ->
+    [polite_and_detailed_message(I) || I <- [1,2,3,4,5]].