PART I
Warm-up
Reconnect with a useful idea before starting instructions and observable results. 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
Find a revealing case, not just another case
A boundary case sits at a meaningful edge of a rule. For addition over signed integers, zero is an identity case: it should leave the other input unchanged. Opposite values test cancellation. These cases reveal different mistakes from repeatedly adding two positive numbers.
For add(0,7), binding gives a = 0 and b = 7, so the return is 7. For add(7,0), the result is also 7. For add(-7,7), the values cancel to 0. An accidental helper that returns only b would pass the first case but fail the second; an accidental multiplication would return 0 for both zero cases.
Stay inside the stated integer domain. This source does not establish an overflow policy for arbitrarily large i32 sums, so do not label a guessed wraparound as a passing result. A careful boundary plan can identify an unresolved case without inventing execution semantics.
Worked reasoning and supplied artifact
fnc add(a: i32, b: i32) -> i32 {
return a + b;
}
fnc main() -> i32 {
return add(2, 3);
}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 add(a: i32, b: i32) -> i32 {Read the function name, its parameter names/types and the result type after ->. This is the contract the body must satisfy.
return a + b;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.
fnc main() -> i32 {Read the function name, its parameter names/types and the result type after ->. This is the contract the body must satisfy.
return add(2, 3);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
Make three columns: inputs, expected sum, mistake this case can expose. Fill rows (0,7), (7,0) and (-7,7).
- 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: Snack-shop calculator. Build a small, understandable change around instructions and observable results.
Design four paper acceptance cases for an inventory adjustment: ordinary addition, zero adjustment, zero starting stock, and a negative adjustment. Identify which cases test arithmetic only and whether the inventory policy would need extra validation.
What to produce
Four expected arithmetic results plus a note that mathematical correctness alone does not establish valid stock policy.
- 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.
Need a hint?
For add(0,7), binding gives a = 0 and b = 7, so the return is 7. For add(7,0), the result is also 7. For add(-7,7), the values cancel to 0. An accidental helper that returns only b would pass the first case but fail the second; an accidental multiplication would return 0 for both zero cases.
Stay inside the stated integer domain. This source does not establish an overflow policy for arbitrarily large i32 sums, so do not label a guessed wraparound as a passing result. A careful boundary plan can identify an unresolved case without inventing execution semantics.
Original learning-path task and reference
In a rhythm-game audio editor, demonstrate instructions and observable results. Add normal, boundary, and invalid-input cases and explain expected behavior. Include .ws source and a host-resource contract; compare at least one normal case and one edge case.
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.
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.
- Find a revealing case, not just another case
- A boundary case sits at a meaningful edge of a rule. For addition over signed integers, zero is an identity case: it should leave the other input unchanged. Opposite values test cancellation. These cases reveal different mistakes from repeatedly adding two positive numbers.
- Separate source-backed behavior, host requirements and untested predictions.
One small recap task
Give a case that distinguishes addition from multiplication and say why.
This marks your personal practice record only. It is not a certification or an official workspace assessment.