Compose playback controls, device recovery contracts, and event cleanup — Discover and trace

PART I

Warm-up

Reconnect with a useful idea before starting compose playback controls, device recovery contracts, and event cleanup. 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

Separate load, configuration and playback outcomes

Proposed WAUDIO describes native audio integration, including MP3 and WAV rather than MP4 support. Loading, configuration, permission and playback are separate outcomes. Every device or control behavior in these exercises is a supplied host contract; no guessed audio methods or real playback are used.

Host contract: load chime.wav succeeds, volume0.5 is valid, and a later explicit play request is denied by device policy. Loading does not itself play audio. No audio runtime is available on the school site.

Worked reasoning: The asset becomes available after load and receives configuration, but denial means playback is not confirmed. A visual status should say Sound unavailable rather than Played. The native host owns decoding and device access.

Failed alternative: Treating successful load as successful playback skips a separate policy and effect boundary.

Worked reasoning and supplied artifact

Asset:chime.wav
Load:accepted
Volume0.5:valid
Play:denied
Predicted status:Sound unavailable
Confirmed audible result:none supplied

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: Media operations console. Build a small, understandable change around compose playback controls, device recovery contracts, and event cleanup.

Trace alert.wav with load success, volume0.7 accepted and playback device unavailable. List each outcome without collapsing them.

What to produce

A load/configure/play evidence ledger with an honest visible status.

• 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 wdb;
domain Inventory {
    const lowStock = wdb.query({
        from: products,
        select: [id, name, stock],
        where: [[ stock < 10 ]],
        order: { by: stock, direction: ascending }
    });
}

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.

• Separate load, configuration and playback outcomes
• Trace alert.wav with load success, volume0.7 accepted and playback device unavailable. List each outcome without collapsing them.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Keep each native audio boundary as its own result row.

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