three alternatives for breaking out of embedded for loops

embedded_loops.cpp

#include <iostream>

int main(int argc, char* argv[]) {
    {
        // a typical embedded loop check can require a check for success and
        // multiple checks to unroll
        bool success = false;
        int i = 0, j = 0;
        for (i = 0; i < 50; ++i) {
            for (j = 0; j < 50; ++j) {
                // check if we succeed at some task using i and j
                success = i * j > 48 * 48;

                // if we succeed then break out of j loop
                if (success) break;
            }

            // if we succeed then break out of i loop
            if (success) break;
        }
        // congratulate ourselves for our great success
        if (success) {
            std::cout << i << "," << j << std::endl;
        }
    }

    {
        // a goto can do this pretty easily; goto is also relatively safe
        int i = 0, j = 0;
        for (i = 0; i < 50; ++i) {
            for (j = 0; j < 50; ++j) {
                // check if we succeed at some task using i and j
                if (i * j > 48 * 48) {
                    goto success;
                }
            }
        }
        goto fail;
    success:
        // congratulate ourselves for our great success
        std::cout << i << "," << j << std::endl;
        // failure case requires this :; to have a nonempty line afterwards
    fail:;
    }

    {
        // an anonymous lambda function lets us do this in a nicely scoped way
        // that is perhaps more readable. the lambda with return lets us define
        // the scope to break out of
        // We can use C++ if statements with initalizers too :)
        if (
            int i = 0, j = 0; [&i, &j]() -> bool {
                for (i = 0; i < 50; ++i) {
                    for (j = 0; j < 50; ++j) {
                        // check if we succeed at some task using i and j
                        if (i * j > 48 * 48) {
                            return true;
                        }
                    }
                }
                return false;
            }()) {
            // congratulate ourselves for our great success
            std::cout << i << "," << j << std::endl;
        }
    }
}