try / catch / throw

Handling Errors Gracefully

#include <stdexcept>

double divide(double a, double b) {
    if (b == 0) throw runtime_error("Division by zero!");
    return a / b;
}

try {
    cout << divide(10, 2);   // 5
    cout << divide(10, 0);   // throws!
} catch (const runtime_error& e) {
    cerr << "Error: " << e.what() << endl;
}
// Program continues after the catch block

Multiple catch blocks

try {
    // ...
} catch (const out_of_range& e) {
    // handle specific case
} catch (const runtime_error& e) {
    // handle runtime errors
} catch (...) {
    // catch everything else
}

RAII: cleanup is automatic

When an exception unwinds the stack, destructors run for all local objects — files close, memory frees, locks release — automatically.

Your Task

Write safeAt(vector<int> v, int i) that returns v[i], but throws out_of_range("index out of range") if i is out of bounds.