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Update Explanation for - ch10-01-generics.toml (Quiz 1) #314

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Update Explanation for - ch10-01-generics.toml (Quiz 1) #314

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a9183a6
Update ch10-01-generics.toml
ss-deshmukh Jun 18, 2025
c0ac297
Merge branch 'cognitive-engineering-lab:main' into main
ss-deshmukh Sep 26, 2025
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7 changes: 5 additions & 2 deletions quizzes/ch10-01-generics.toml
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Expand Up @@ -28,8 +28,11 @@ fn mystery<T>(x: T) -> T {
}
```

The function could of course panic or print, but the return value can only be the input. `mystery` does not know
what type `T` is, so there is no way for `mystery` to generate or mutate a value of `T`.
Since the function mystery<T>(x: T) -> T has no trait bounds and 'T' is an unknown type, the function doesnt
know which operations 'T' supports and thus cannot generate or mutate a value of 'T' (+, ==, or .clone() to
change the value of x). Additionally since we also assume that it has no unsafe code thus it's forced to just
return the input x unchanged, making x = 3.

See [Theorems for free!](https://dl.acm.org/doi/pdf/10.1145/99370.99404) for more examples of this idea.

**3 really is the correct answer! If you disagree with the answer, please don't submit a bug report!**
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