Flexical scoping

#include <iostream>
using namespace std;

// Assume that we've got some globally-available logging, stats, and profiling
// things. We might use them from lots of places, like libraries that don't
// know if they're being used by a web server, an RPC server, or a one-off
// script. Our web server wants to tie log messages that result from a request
// to information about the request (the path, the user ID, etc.). How do?
//
// One option would be to pass around a state object, but this just sucks.
// Everything that might ever log anything would need it.
//
// So, what if Team had a kind of box that could be assigned to, whose value
// would be visible from that context and any contexts which inherited from it?
// Different values could be simultaneously visible from different contexts.
//
//                  +--------+
//                  | main() |
//                  +--------+
//           /-----------|-----------\
//     +---------+  +---------+  +---------+
//     | request |  | request |  | request |
//     +---------+  +---------+  +---------+
//          |            |            |
//        assign       assign       assign
//     logging info logging info logging info
//          |            |            |
//         ...          ...          ...
//          |            |            |
//      +-------+    +-------+    +-------+
//      | log() |    | log() |    | log() |
//      +-------+    +-------+    +-------+

class {

    string prefix() {
        return "";
    }

    public:
    void warn(const char *message) {
        cout << prefix() << message << endl;
    }

} log;

namespace worklib {
    void doWork() {
        log.warn("Working on user...");
    }
}


int main() {

    HTTP::Server([](auto req, auto res) {
        log.setPrefix(req.path);
        doWork();
    });
}