Respond to application readiness — Boundary detective

PART I

Warm-up

Reconnect with a useful idea before starting respond to application readiness. In one or two sentences, describe the input, output or host boundary from the previous exercise that this lesson builds on. If you are arriving directly, skim the worked example first; there is no locked prerequisite.

A rough note is enough. You can revise it after the example.

PART II

Instruction & guided example

Handle registration after readiness

Readiness is a transition, not an import. An application declaration registers a response. Registration, delivery of app.ready, and execution of the response are separate moments. The supplied exercise host decides delivery timing and whether registration after readiness receives a replay. Never infer replay or exactly-once delivery from the callback syntax.

Host A replays readiness to late registrations. Host B only delivers future events. Both became ready at t=2; this mod registers at t=5. No readiness-query API is supplied.

Use an event ledger: time, delivered event, owner state, response, and visible state. A row that registers a callback has no delivered event. Mark the visible state unchanged until a host-delivered event authorizes the response. Worked case: For A, registration at t=5 is followed by a replay and the response may run. For B, there is no future ready event, so delivery cannot be inferred. The same configuration has different justified predictions under different contracts.

Compare the tempting alternative: Claiming all event systems replay silently adds a guarantee that Host B never made. Polling an invented isReady method is also unsupported.

Worked reasoning and supplied artifact

// Paper trace / supplied exercise-host contract; no execution claimed.
// Host A replays readiness to late registrations. Host B only delivers future events. Both became ready at t=2; this mod registers at t=5. No readiness-query API is supplied.
// For A, registration at t=5 is followed by a replay and the response may run. For B, there is no future ready event, so delivery cannot be inferred. The same configuration has different justified predictions under different contracts.

Illustrative example from the proposed WillowScript design. The language and WUIX/WMATH/WDB/WAUDIO/WTMP services are not implemented in the supplied source. This site has no interpreter, VM or native host and does not execute or certify the snippet.

Try the guided change

Reconstruct the supplied worked case first: list its inputs, intermediate decisions and final artifact. Compare each row with the explanation and identify exactly where the rejected alternative fails. Then use the changed inputs in Part IV for independent work.

• Write the supplied inputs and initial state before following the example.
• Reconstruct each intermediate calculation or host decision, then compare with the worked artifact.
• Explain why the contrasting alternative fails before attempting the changed inputs in Part IV.

PART III

Take a breather

Step back after the guided example. Look away from the screen, stretch, or reread your prediction. This is an optional learning pause, not a timer or an assessment gate.

When you return, try to name the lesson’s key idea without copying its wording. If that feels difficult, return to Part II and trace one line rather than restarting the entire lesson.

PART IV

Independent practice

Project context: Support request workflow. Build a small, understandable change around respond to application readiness.

Write two host-contract rows and identify the missing capability that would make late registration reliable under B.

What to produce

An A/B behavior comparison and one explicit unresolved requirement.

• State the intended behavior in a sentence before editing.
• Use only source-backed syntax and the host services whose contract you have been given.
• Record a normal case and a boundary or unavailable-resource case.
• Label hand predictions separately from anything actually measured in a supplied toolchain.

Syntax colors are a reading aid, not a compiler. The line you are editing stays uncolored until you move to a different line; capitalization is never changed. Drafts stay on this browser and code is not executed.

import wuix.widget;
import app;
domain Workspace {
    const application = Application({
        name: "Workspace",
        window: { title: "Dashboard", size: [1280, 800] },
        events: {
            "app.ready": fnc() -> void { console.log("Ready"); }
        }
    });
}

PART V

Self-check

Use this check to notice what to revisit. It does not award a private course grade, block another page or claim to verify compiled code. Every answer has a learning explanation.

You may keep exploring even if you are unsure. Use the hint, compare the trace, and revise your explanation.

PART VI

Recap & small task

Bring the idea back to the mod feature you are building. A useful recap connects the mechanism to a decision you can make in your own code.

• Handle registration after readiness
• Write two host-contract rows and identify the missing capability that would make late registration reliable under B.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Write the replay rule your utility requires from its host.

This marks your personal practice record only. It is not a certification or an official workspace assessment.