%%% -*- erlang-indent-level: 2 -*-
%%%-------------------------------------------------------------------
%%% Author: Kostis Sagonas
%%%
%%% Contains tests for correct handling of guards and guard BIFs.
%%%-------------------------------------------------------------------
-module(basic_guards).
-export([test/0]).
%% Prevent the inlining of the following functions
-export([bad_arith/0, bad_tuple/0, is_strange_guard/0]).
test() ->
ok = guard0(4.2),
ok = guard1([foo]),
ok = test_guard2(),
ok = test_guard3(),
ok = test_guard4(),
ok = test_is_boolean(),
ok = test_bad_guards(),
ok.
%%--------------------------------------------------------------------
guard0(X) when X /= 0, is_float(X) ->
ok.
guard1(X) when is_atom(X) orelse is_float(X) ->
error1;
guard1(X) when is_reference(hd(X)) ->
error2;
guard1(X) when is_integer(hd(X)) ->
error3;
guard1(X) when hd(X) == foo ->
ok.
%%--------------------------------------------------------------------
test_guard2() ->
ok1 = guard2(true),
not_boolean = guard2(42),
ok2 = guard2(false),
ok.
guard2(X) when X -> % gets transformed to: is_boolean(X), X =:= true
ok1;
guard2(X) when X =:= false ->
ok2;
guard2(_) ->
not_boolean.
%%--------------------------------------------------------------------
-define(is_foo(X), (is_atom(X) or (is_tuple(X) and (element(1, X) =:= 'foo')))).
test_guard3() ->
no = f('foo'),
yes = f({'foo', 42}),
no = f(42),
ok.
f(X) when ?is_foo(X) -> yes;
f(_) -> no.
%%--------------------------------------------------------------------
-define(EXT_REF, <<131,114,0,3,100,0,19,114,101,102,95,116,101,115,116,95,98,117,103,64,103,111,114,98,97,103,2,0,0,0,125,0,0,0,0,0,0,0,0>>).
test_guard4() ->
yes = is_ref(make_ref()),
no = is_ref(gazonk),
yes = is_ref(an_external_ref(?EXT_REF)),
ok.
is_ref(Ref) when is_reference(Ref) -> yes;
is_ref(_Ref) -> no.
an_external_ref(Bin) ->
binary_to_term(Bin).
%%--------------------------------------------------------------------
test_is_boolean() ->
ok = is_boolean_in_if(),
ok = is_boolean_in_guard().
is_boolean_in_if() ->
ok1 = tif(true),
ok2 = tif(false),
not_bool = tif(other),
ok.
is_boolean_in_guard() ->
ok = tg(true),
ok = tg(false),
not_bool = tg(other),
ok.
tif(V) ->
Yes = yes(), %% just to prevent the optimizer removing this
if
%% the following line generates an is_boolean instruction
V, Yes == yes ->
%% while the following one does not (?!)
%% Yes == yes, V ->
ok1;
not(not(not(V))) ->
ok2;
V ->
ok3;
true ->
not_bool
end.
tg(V) when is_boolean(V) ->
ok;
tg(_) ->
not_bool.
yes() -> yes.
%%--------------------------------------------------------------------
%% original test by Bjorn G
test_bad_guards() ->
ok = bad_arith(),
ok = bad_tuple(),
ok = is_strange_guard(),
ok.
bad_arith() ->
13 = bad_arith1(1, 12),
42 = bad_arith1(1, infinity),
42 = bad_arith1(infinity, 1),
42 = bad_arith2(infinity, 1),
42 = bad_arith3(inf),
42 = bad_arith4(infinity, 1),
ok.
bad_arith1(T1, T2) when (T1 + T2) < 17 -> T1 + T2;
bad_arith1(_, _) -> 42.
bad_arith2(T1, T2) when (T1 * T2) < 17 -> T1 * T2;
bad_arith2(_, _) -> 42.
bad_arith3(T) when (bnot T) < 17 -> T;
bad_arith3(_) -> 42.
bad_arith4(T1, T2) when (T1 bsr T2) < 10 -> T1 bsr T2;
bad_arith4(_, _) -> 42.
bad_tuple() ->
error = bad_tuple1(a),
error = bad_tuple1({a, b}),
x = bad_tuple1({x, b}),
y = bad_tuple1({a, b, y}),
ok.
bad_tuple1(T) when element(1, T) =:= x -> x;
bad_tuple1(T) when element(3, T) =:= y -> y;
bad_tuple1(_) -> error.
is_strange_guard() when is_tuple({1, bar, length([1, 2, 3, 4]), self()}) -> ok;
is_strange_guard() -> error.
