0008188: Support for function literals

(0016522)
Jens Grabowski (manager)
05-09-2023 11:06

TTF discussion: More elaborated example needed.

(0016549)
Matthias Simon (developer)
08-11-2023 12:35

Function literals are evaluated lazily and capture their context. This makes implementation of deferred functions feasible. For example:

    type function CancelFunc();

    testcase Example() runs on MTC {
        // start fixtures
        var cancel := SetupDatabase();

        // do some testing

        // handle graceful shutdown
        cancel();
    }

    function SetupDatabase() return CancelFunc
    {
        var db := DatabaseComponent.create;
        db.start(listen());
        return function() {
            db.stop; // Captures db and allows to call methods, locally
        }
    }

Another use-case is parametrizing callbacks:

    module Service
    {
        type component Component { /* ... */ }

        function Start(in ExitFunc ef := withSuccess) return Component
        {
            var c := Component.create;
            c.start(mainLoop(ef));
            return c;
        }

        private function mainLoop(ExitFunc ef) runs on Component {
            p.receive(ProcessState:{started := ?});
            log("Service is up and running");

            var ExitCode ec;
            p.receive(ProcessState:{exited := ?}) -> value ec;
            f(ec);
        }

        type function ExitFunc(ExitCode ec) runs on Component;

        type enumerated ExitCode {
            SUCCESS(0),
            ERROR(1..127),
            SIGTERM(-15),
            SIGKILL(-9),
        }

        group helpers
        {
            function withSuccess(in ExitCode ec) runs on Component {
                if (ec != SUCCESS) {
                    setverdict(fail, "want=0, got=" & ec);
                    stop;
                }
            }

            function withError(in ExitCode ec) runs on Component {
                if (ec != ERROR) {
                    setverdict(fail, "want!=0, got=" & ec);
                    stop;
                }
            }

            function withSignal(in ExitCode sig) return ExitFunc
            {
                return function(in ExitCode ec) runs on Component {
                    if (ec != sig) {
                        setverdict(fail, "want=" & sig, got=" & ec);
                        stop;
                    }
                }
            }

            function withTimeout(in float duration) return ExitFunc
            {
                return function(in ExitCode ec) runs on Component {
                    // ...
                }
        }
    }

    module Example
    {
        testcase SunnyDay()
        {
            var service1 := Service.Start();
            var service2 := Service.Start(Service.withError);

            // do some API testing...

            all components.done;
        }

        testcase ResilianceTest_ServiceCrashes()
        {
            var service1 := Service.Start(Service.withSignal(Service.SIGTERM));
            var service2 := Service.Start(Service.withTimeout(60.0));

            // do some API testing...

            all components.done;
        }

    }

(0016569)
Gusztáv Adamis (developer)
09-11-2023 20:52

The problems in examples can be solved with the existing TTCN-3 instructions.

(0016610)
Olivier Genoud (administrator)
26-01-2024 16:28

We assume/expect that this CR will not become part of the core language but will become part of an extension or be added to an extension (e.g. OO extension).

Issue History
Date Modified	Username	Field	Change
11-01-2023 12:57	Matthias Simon	New Issue
05-09-2023 11:06	Jens Grabowski	Note Added: 0016522
05-09-2023 11:07	Jens Grabowski	Assigned To	=> Matthias Simon
05-09-2023 11:07	Jens Grabowski	Status	new => assigned
08-11-2023 12:35	Matthias Simon	Note Added: 0016549
08-11-2023 13:54	Jens Grabowski	Assigned To	Matthias Simon => Jens Grabowski
08-11-2023 13:54	Jens Grabowski	Assigned To	Jens Grabowski => Matthias Simon
08-11-2023 13:54	Jens Grabowski	Assigned To	Matthias Simon => Gusztáv Adamis
09-11-2023 20:52	Gusztáv Adamis	Note Added: 0016569
26-01-2024 16:28	Olivier Genoud	Note Added: 0016610

Notes
(0016522) Jens Grabowski (manager) 05-09-2023 11:06	TTF discussion: More elaborated example needed.

(0016549) Matthias Simon (developer) 08-11-2023 12:35	Function literals are evaluated lazily and capture their context. This makes implementation of deferred functions feasible. For example: type function CancelFunc(); testcase Example() runs on MTC { // start fixtures var cancel := SetupDatabase(); // do some testing // handle graceful shutdown cancel(); } function SetupDatabase() return CancelFunc { var db := DatabaseComponent.create; db.start(listen()); return function() { db.stop; // Captures db and allows to call methods, locally } } Another use-case is parametrizing callbacks: module Service { type component Component { /* ... */ } function Start(in ExitFunc ef := withSuccess) return Component { var c := Component.create; c.start(mainLoop(ef)); return c; } private function mainLoop(ExitFunc ef) runs on Component { p.receive(ProcessState:{started := ?}); log("Service is up and running"); var ExitCode ec; p.receive(ProcessState:{exited := ?}) -> value ec; f(ec); } type function ExitFunc(ExitCode ec) runs on Component; type enumerated ExitCode { SUCCESS(0), ERROR(1..127), SIGTERM(-15), SIGKILL(-9), } group helpers { function withSuccess(in ExitCode ec) runs on Component { if (ec != SUCCESS) { setverdict(fail, "want=0, got=" & ec); stop; } } function withError(in ExitCode ec) runs on Component { if (ec != ERROR) { setverdict(fail, "want!=0, got=" & ec); stop; } } function withSignal(in ExitCode sig) return ExitFunc { return function(in ExitCode ec) runs on Component { if (ec != sig) { setverdict(fail, "want=" & sig, got=" & ec); stop; } } } function withTimeout(in float duration) return ExitFunc { return function(in ExitCode ec) runs on Component { // ... } } } module Example { testcase SunnyDay() { var service1 := Service.Start(); var service2 := Service.Start(Service.withError); // do some API testing... all components.done; } testcase ResilianceTest_ServiceCrashes() { var service1 := Service.Start(Service.withSignal(Service.SIGTERM)); var service2 := Service.Start(Service.withTimeout(60.0)); // do some API testing... all components.done; } }

(0016569) Gusztáv Adamis (developer) 09-11-2023 20:52	The problems in examples can be solved with the existing TTCN-3 instructions.

(0016610) Olivier Genoud (administrator) 26-01-2024 16:28	We assume/expect that this CR will not become part of the core language but will become part of an extension or be added to an extension (e.g. OO extension).

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