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2010-05-25T14:21:06Z

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2010-05-25T10:23:59Z

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==An exception can be thrown from outside the try block==

<source lang="cpp">
#include <iostream>
using namespace std;
void myFunction(int test)
{
cout << "Inside myFunction, test is: " << test << "\n";
if(test) throw test;
}
int main()
{
cout << "Start\n";
try {
cout << "Inside try block\n";
myFunction(0);
myFunction(1);
myFunction(2);
}
catch (int i) {
cout << "Caught an exception -- value is: ";
cout << i << "\n";
}
cout << "End";
return 0;
}

</source>

==A try/catch can be inside a function other than main().==

<source lang="cpp">
#include <iostream>
using namespace std;

void myFunction(int test)
{
try{
if(test)
throw test;
}
catch(int i) {
cout << "Caught One! Ex. #: " << i << "\n";
}
}
int main()
{
cout << "start\n";
myFunction(1);
myFunction(2);
myFunction(0);
myFunction(3);
cout << "end";
return 0;
}

</source>

==Catch exception: int i ==

<source lang="cpp">
#include <iostream>
using namespace std;
int main()
{
cout << "Start\n";
try {
cout << "Inside try block\n";
cout << "Still inside try block\n";
}catch (int i) { // catch an error
cout << "Caught an exception and value is: ";
cout << i << endl;
}
cout << "End";
return 0;
}

</source>

==Different types of exceptions can be caught.==

<source lang="cpp">
#include <iostream>
using namespace std;

void myFunction(int test)
{
try{
if(test)
throw test;
else
throw "Value is zero";
}catch(int i) {
cout << "Caught Exception #: " << i << "\n";
}catch(const char *str) {
cout << "Caught a string: ";
cout << str << "\n";
}
}
int main()
{
cout << "Start\n";
myFunction(1);
myFunction(2);
myFunction(0);
myFunction(3);
cout << "End";
return 0;
}

</source>

==Handle exceptions thrown by new.==

<source lang="cpp">
#include <iostream>
#include <new>
using namespace std;
int main()
{
int *p, i;
try {
p = new int[32]; // allocate memory for 32-element int array
} catch (bad_alloc xa) {
cout << "Allocation failure.\n";
return 1;
}
for(i = 0; i <32; i++)
p[i] = i;
for(i = 0; i <32; i++)
cout << p[i] << " ";
delete [] p; // free the memory
return 0;
}

</source>

==Matching Any Exception==

<source lang="cpp">
#include <fstream>
#include <iostream>
#include <vector>
#include <string>
#include <stdexcept>
using namespace std;
void readIntegerFile(const string& fileName, vector<int>& dest)
{
ifstream istr;
int temp;
istr.open(fileName.c_str());
if (istr.fail()) {
throw invalid_argument("");
}
while (istr >> temp) {
dest.push_back(temp);
}
if (istr.eof()) {
istr.close();
} else {
istr.close();
throw runtime_error("");
}
}
int main(int argc, char** argv)
{
vector<int> myInts;
const string fileName = "IntegerFile.txt";
try {
readIntegerFile(fileName, myInts);
} catch (...) {
cerr << "Error reading or opening file " << fileName << endl;
exit (1);
}
for (size_t i = 0; i < myInts.size(); i++) {
cout << myInts[i] << " ";
}
cout << endl;
return (0);
}

</source>

==No Exception Handling==

<source lang="cpp">
#include <fstream>
#include <iostream>
#include <vector>
#include <string>
using namespace std;
void readIntegerFile(const string& fileName, vector<int>& dest)
{
ifstream istr;
int temp;
istr.open(fileName.c_str());
while (istr >> temp) {
dest.push_back(temp);
}
}
int main(int argc, char** argv)
{
vector<int> myInts;
const string fileName = "IntegerFile.txt";
readIntegerFile(fileName, myInts);
for (size_t i = 0; i < myInts.size(); i++) {
cout << myInts[i] << " ";
}
cout << endl;
return (0);
}

</source>

==Restricting function throw types.==

<source lang="cpp">
#include <iostream>
using namespace std;

void myFunction(int test) throw(int, char, double)
{
if(test==0)
throw test; // throw int
if(test==1)
throw "a"; // throw char
if(test==2)
throw 333.23; // throw double
}
int main()
{
cout << "start\n";
try{
myFunction(0);
}
catch(int i) {
cout << "Caught an integer\n";
}
catch(char c) {
cout << "Caught char\n";
}
catch(double d) {
cout << "Caught double\n";
}
try{
myFunction(1);
}
catch(int i) {
cout << "Caught an integer\n";
}
catch(char c) {
cout << "Caught char\n";
}
catch(double d) {
cout << "Caught double\n";
}
try{
myFunction(2);
}
catch(int i) {
cout << "Caught an integer\n";
}
catch(char c) {
cout << "Caught char\n";
}
catch(double d) {
cout << "Caught double\n";
}

cout << "end";
return 0;
}

</source>

==Rethrowing an Exception==

<source lang="cpp">
#include <iostream>
using namespace std;
void myFunction()
{
try {
throw "hello"; // throw a char *
}
catch(const char *) { // catch a char *
cout << "Caught char * inside myFunction\n";
throw ; // rethrow char * out of function
}
}
int main()
{
cout << "Start\n";
try{
myFunction();
}
catch(const char *) {
cout << "Caught char * inside main\n";
}
cout << "End";
return 0;
}

</source>

==Terminate Handler==

<source lang="cpp">
#include <fstream>
#include <iostream>
#include <vector>
#include <string>
#include <stdexcept>
#include <exception>
using namespace std;
void readIntegerFile(const string& fileName, vector<int>& dest)
{
ifstream istr;
int temp;
istr.open(fileName.c_str());
if (istr.fail()) {
throw invalid_argument("");
}
while (istr >> temp) {
dest.push_back(temp);
}
if (istr.eof()) {
istr.close();
} else {
istr.close();
throw runtime_error("");
}
}
void myTerminate()
{
cout << "Uncaught exception!\n";
exit(1);
}
int main(int argc, char** argv)
{
vector<int> myInts;
const string fileName = "IntegerFile.txt";
set_terminate(myTerminate);
readIntegerFile(fileName, myInts);
for (size_t i = 0; i < myInts.size(); i++) {
cerr << myInts[i] << " ";
}
cout << endl;
return (0);
}

</source>

==Throw and catch an exception inside a function==

<source lang="cpp">
#include <iostream>
#include <cstdlib>
using namespace std;
double divide(double a, double b)
{
try {
if(!b) throw(b);
}
catch(double) {
cout << "Cannot divide by zero.\n";
exit(1);
}
return a/b;
}
int main()
{
cout << divide(10.0, 2.5) << endl;
cout << divide(10.0, 0.0);
return 0;
}

</source>

==Uses catch(...) to catch all exceptions==

<source lang="cpp">

#include <iostream>
using namespace std;
void myFunction(int test)
{
try{
if(test==0) // throw int
throw test;
if(test==1) // throw char
throw "a";
if(test==2) // throw double
throw 123.23;
} catch(int i) { // catch an int exception
cout << "Caught " << i << "\n";
} catch(...) { // catch all other exceptions
cout << "Caught One!\n";
}
}
int main()
{
cout << "start\n";
myFunction(0);
myFunction(1);
myFunction(2);
cout << "end";
return 0;
}

</source>

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