Add tutorial on narrowing conversions for wide pointers - #184
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jbcoe
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Aug 27, 2026
| // Handles an AnimalPtr by looking up (or, on first use, building) a | ||
| // cached BirdVtable for its vtable_, rather than owning one itself or | ||
| // wrapping the AnimalPtr. | ||
| BirdPtr(AnimalPtr* animal) |
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This needs to be AnimalPtr - take pointers, even wide pointers, by value.
jbcoe
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Aug 27, 2026
| EXPECT_EQ(bird.noise(), "Screech"); | ||
| }); | ||
| } | ||
| // jthreads join automatically when destroyed, so no explicit join loop. |
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Remove this redundant comment.
jbcoe
commented
Aug 27, 2026
| AnimalPtr eagle_view(&eagle); | ||
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| // Two lookups against the same AnimalPtr share a cache entry; a | ||
| // different AnimalPtr gets its own. |
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Remove this redundant comment.
jbcoe
commented
Aug 27, 2026
| EXPECT_EQ(duck_view.noise(), "Quack"); | ||
| EXPECT_EQ(duck_view.identity(), "Duck"); | ||
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| // Constructed from a pointer to duck_view, not from `duck` itself. |
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Remove this redundant comment.
jbcoe
commented
Aug 27, 2026
| std::string_view identity() const { return "Eagle"; } | ||
| }; | ||
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| // BirdVtable is narrower than AnimalVtable in the same way a Bird is a |
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Rewrite this mostly redundant comment.
jbcoe
commented
Aug 27, 2026
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| // A follow-up to the tutorial on polymorphism. We construct a narrow |
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Rewrite this comment to avoid clumsy overloading and re-use of wide and narrow.
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