### A free/open-source library for quantitative finance

tracing_example.cpp

This code exemplifies how to insert trace statements to follow the flow of program execution. When compiler under gcc 3.3 and run, the following program will output the following trace:

            trace[1]: Entering int main()
            trace[2]: Entering int foo(int)
            trace[3]: Entering int Foo::bar(int)
            trace[3]: i = 21
            trace[3]: At line 16 in tracing_example.cpp
            trace[3]: Wrong answer
            trace[3]: i = 42
            trace[3]: Exiting int Foo::bar(int)
            trace[3]: Entering int Foo::bar(int)
            trace[3]: i = 42
            trace[3]: At line 13 in tracing_example.cpp
            trace[3]: Right answer, but no question
            trace[3]: i = 42
            trace[3]: Exiting int Foo::bar(int)
            trace[2]: Exiting int foo(int)
            trace[1]: Exiting int main()

Of course, a word of warning must be added: adding so much tracing to your code might degrade its readability, at least until we devise an Emacs macro to hide trace statements with a couple of keystrokes.

    #include <ql/quantlib.hpp>

    using namespace QuantLib;

    namespace Foo {

        int bar(int i) {
            QL_TRACE_ENTER_FUNCTION;
            QL_TRACE_VARIABLE(i);

            if (i == 42) {
                QL_TRACE_LOCATION;
                QL_TRACE("Right answer, but no question");
            } else {
                QL_TRACE_LOCATION;
                QL_TRACE("Wrong answer");
                i *= 2;
            }

            QL_TRACE_VARIABLE(i);
            QL_TRACE_EXIT_FUNCTION;
            return i;
        }

    }

    int foo(int i) {
        using namespace Foo;
        QL_TRACE_ENTER_FUNCTION;

        int j = bar(i);
        int k = bar(j);

        QL_TRACE_EXIT_FUNCTION;
        return k;
    }

    int main() {

        QL_TRACE_ENABLE;

        QL_TRACE_ENTER_FUNCTION;

        int i = foo(21);

        QL_TRACE_EXIT_FUNCTION;
        return 0;
    }