/*
* Copyright 2011 Steven Gribble
*
* This file is the solution to an exercise problem posed during
* one of the UW CSE 333 lectures (333exercises).
*
* 333exercises is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* 333exercises is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with 333exercises. If not, see .
*/
#include
#include
#include
#include
#include
#include "complex.h"
// We use the following global variable to check whether
// a divide-by-zero exception is expected or not. We'll
// start out not expecting it, and we'll set this to 1 when
// we test a complex division that should trigger a divide by
// zero exception.
static int expect_divzero = 0;
// This is a "signal handler"; in main(), we register this function
// with the operating system using the "sigaction()" system call.
// Do a "man sigaction" to learn about it.
static void handle_divzero(int sig, siginfo_t *si, void *data) {
assert(expect_divzero == 1);
exit(0); // terminate the process; same as "return 0;" from main
}
// Because floating points are an approximate rather than exact
// representation, you can't directly compare two C doubles and
// expect it to work. Instead, you need to compare for equality
// within some threshold. This helper function DoubleEqualsEpsilon
// and EPSILON #define do this.
#define EPSILON ((double) 0.000000000001)
static int DoubleEqualsEpsilon(double a, double b) {
if (a > b) {
// a > b case
if ((a - b) < EPSILON)
return 1;
return 0;
}
// b <= a case
if ((b - a) < EPSILON)
return 1;
return 0;
}
int main(int argc, char **argv) {
Complex a = {1, 2}, b = {3, 4}, c = {0, 0};
Complex res;
struct sigaction act, oldact;
// register our SIGFPE floating point handler
act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
act.sa_sigaction = &handle_divzero;
assert(sigaction(SIGFPE, &act, &oldact) == 0);
res = ComplexAdd(a, b);
assert(DoubleEqualsEpsilon(res.real, 4.0) == 1);
assert(DoubleEqualsEpsilon(res.imaginary, 6.0) == 1);
res = ComplexSubtract(a, b);
assert(DoubleEqualsEpsilon(res.real, -2.0) == 1);
assert(DoubleEqualsEpsilon(res.imaginary, -2.0) == 1);
res = ComplexMultiply(a, b);
assert(DoubleEqualsEpsilon(res.real, -5) == 1);
assert(DoubleEqualsEpsilon(res.imaginary, 2.0) == 1);
res = ComplexDivide(a, b);
assert(DoubleEqualsEpsilon(res.real, 0.44) == 1);
assert(DoubleEqualsEpsilon(res.imaginary, 0.08) == 1);
// Test the "divide by zero" case. On modern Intel
// machines and Linux, this causes the returned
// Complex to contain the value "NAN" in both the
// real and imaginary components. The
// function "isnan()" is how we compare to NAN.
// But, to be super paranoid, we've also set up
// a signal handler to catch a SIGFPE floating point
// exception (which integer divide by zero throws).
expect_divzero = 1;
res = ComplexDivide(a, c);
assert(isnan(res.real));
assert(isnan(res.imaginary));
return EXIT_SUCCESS;
}