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%%% -*- erlang-indent-level: 2 -*-
%%%-------------------------------------------------------------------
%%% Author: Kostis Sagonas
%%%
%%% Contains code examples that test bignum arithmetic and matching.
%%%-------------------------------------------------------------------
-module(basic_bignums).
-export([test/0, test_bsl/0]).
test() ->
ok = test_ops(),
ok = test_big_fac(),
ok = test_int_overfl_32(),
ok = test_int_overfl_64(),
ok = test_int_overfl_32_guard(),
ok = test_int_overfl_64_guard(),
ok.
%%--------------------------------------------------------------------
%% Define some constants for the tests of arithmetic operators
-define(X, 68719476736).
-define(Y, 98765432101234).
-define(Z, 4722366482869645213696).
-define(W, 339254531512339254531512).
-define(B1, 4398046511104).
-define(B5, 1645504557321206042154969182557350504982735865633579863348609024).
-define(B17, 86182066610968551542636378241108028056376767329454880514019834315878107616003372189510312530372009184902888961739623919010110377987011442493486117202360415845666384627768436296772219009176743399772868636439042064384).
%%--------------------------------------------------------------------
test_ops() ->
ok = test_mult(),
ok = test_div(),
ok = test_round(),
ok = test_trunc(),
ok = test_bsl(),
ok.
test_mult() ->
?Z = mult(?X, ?X),
ok.
mult(X, Y) -> X * Y.
test_div() ->
4 = div_f(339254531512, ?X),
0 = div_f(?Y, ?Y+1),
64 = div_f(?B1, ?X),
?X = div_f(?Z, ?X),
1073741824 = div_f(?Z, ?B1),
ok.
div_f(X, Y) -> X div Y.
test_round() ->
0 = round_f(?Z, ?W),
1 = round_f(?Y, ?Y),
71 = round_f(?W, ?Z),
1437 = round_f(?Y, ?X),
47813960 = round_f(?Z, ?Y),
4936803183406 = round_f(?W, ?X),
ok.
trunc_f(X, Y) -> round(X/Y).
test_trunc() ->
0 = trunc_f(?Z, ?W),
1 = trunc_f(?Y, ?Y),
72 = trunc_f(?W, ?Z),
1437 = trunc_f(?Y, ?X),
47813961 = trunc_f(?Z, ?Y),
4936803183407 = trunc_f(?W, ?X),
ok.
round_f(X, Y) -> trunc(X/Y).
test_bsl() ->
?B1 = bsl_f(1, 42),
?B5 = n(5, fun erlang:'bsl'/2, 1, 42), % use the operator
?B17 = n(17, fun bsl_f/2, 1, 42), % use the local function
ok.
bsl_f(X, Y) -> X bsl Y.
%% applies a binary function N times
n(1, F, X, Y) -> F(X, Y);
n(N, F, X, Y) when N > 1 -> n(N-1, F, F(X, Y), Y).
%%--------------------------------------------------------------------
-define(FAC42, 1405006117752879898543142606244511569936384000000000).
test_big_fac() ->
?FAC42 = fac(42),
ok.
fac(0) -> 1;
fac(N) -> N * fac(N-1).
%%--------------------------------------------------------------------
%% Tests for correct handling of integer overflow
test_int_overfl_32() ->
16#7FFFFFF = add(16#7FFFFFF, 0),
16#8000000 = add(16#8000000, 0),
16#8000001 = add(16#8000000, 1),
case add(16#7FFFFFF, 1) of
16#8000000 -> ok;
-16#7FFFFFF -> error
end.
test_int_overfl_64() ->
16#7FFFFFFFFFFFFFF = add(16#7FFFFFFFFFFFFFF, 0),
16#800000000000000 = add(16#800000000000000, 0),
16#800000000000001 = add(16#800000000000000, 1),
case add(16#7FFFFFFFFFFFFFF, 1) of
16#800000000000000 -> ok;
-16#7FFFFFFFFFFFFFF -> error
end.
add(X, Y) -> X + Y.
%%--------------------------------------------------------------------
%% Tests for correct handling of integer overflow in guards
test_int_overfl_32_guard() ->
ok = overfl_in_guard(16#7ffffff, 0),
ok = overfl_in_guard(16#7ffffff, 16#7ffffff),
ok.
test_int_overfl_64_guard() ->
ok = overfl_in_guard(16#7ffffffffffffff, 0),
ok = overfl_in_guard(16#7ffffffffffffff, 16#7ffffffffffffff),
ok.
overfl_in_guard(X, Y) ->
case ok of
V when X+Y > 12 -> V;
_ -> bad
end.
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