Values, expressions, and arithmetic — Review and demonstrate

PART I

Warm-up

Reconnect with a useful idea before starting values, expressions, and arithmetic. 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.

Recall note

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

PART II

Instruction & guided example

Explain why a calculator formula matches its rule

Review a formula by walking between words, units and operations. A worked result proves one example; the structure explains why the helper is a sensible implementation for the stated domain. Both belong in a reviewable artifact.

For an order of 3 snacks at 80 cents plus a 20-cent bag fee, total(quantity,unitPrice,fee) computes quantity * unitPrice + fee. The intermediate subtotal is 240 cents and the total is 260 cents. Changing quantity to 0 gives 20 under this exact arithmetic rule; whether an empty order should be charged requires a separate business decision.

Do not quietly change the zero-order result to 0 while claiming you preserved the original rule. Either keep the arithmetic rule or explicitly introduce an input-validation decision in a later lesson. A transparent limitation is better than an unexplained special case.

Worked reasoning and supplied artifact

fnc total(quantity: i32, unitPrice: i32, fee: i32) -> i32 {
    return quantity * unitPrice + fee;
}

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.

Walk through the example, one line at a time

fnc total(quantity: i32, unitPrice: i32, fee: i32) -> i32 {
Read the function name, its parameter names/types and the result type after ->. This is the contract the body must satisfy.
return quantity * unitPrice + fee;
Evaluate the following expression using the current values, then send its result to the caller. Explain the value; do not confuse it with printed output.
}
Close the nested block or value begun earlier. Match it to its opening boundary to keep the structure readable.

Try the guided change

Annotate each parameter’s unit and explain the two operations for (3,80,20).

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.

Prediction or guided notes

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.

Your drafts remain here. Continue whenever you are ready.

PART IV

Independent practice

Project context: Snack-shop calculator. Build a small, understandable change around values, expressions, and arithmetic.

Prepare a calculator review card for 5 tickets at 120 cents with a 35-cent booking fee. Add quantity zero and fee zero cases, explain each expected result, and list input constraints you would require before use in a real shop.

What to produce

Formula, unit annotations, predictions 635/35/600, and explicit constraints rather than fabricated validation.

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.

Your .ws practice draft

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.

Need a hint?

Original learning-path task and reference

In a community library utility, demonstrate values, expressions, and arithmetic. Submit source, acceptance cases, and an explanation proving the section objective. Include .ws source and a host-resource contract; compare at least one normal case and one edge case.

fnc add(a: i32, b: i32) -> i32 {
    return a + b;
}
fnc main() -> i32 {
    return add(2, 3);
}

Where the original task needs a host API that is not supplied here, write the contract and predictions. Do not invent a runtime result.

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.

Why should the empty-order behavior be recorded explicitly?The arithmetic rule still adds the fee even when quantity is zeroZero makes all expressions invalidThe website automatically charges the fee

Explain a normal or boundary case

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.

Explain why a calculator formula matches its rule
Review a formula by walking between words, units and operations. A worked result proves one example; the structure explains why the helper is a sensible implementation for the stated domain. Both belong in a reviewable artifact.
Separate source-backed behavior, host requirements and untested predictions.

One small recap task

State one constraint a real currency calculation needs beyond the integer expression.

Your recap

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