The Three Layers of Headers A Curious Discovery

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" summary

Claim: any header can be decomposed into three layers of headers — a top layer of forward declarations, a middle interface file with type and free‑function declarations, and a bottom layer of inline implementations and globals. Doing this breaks cyclical include chains (example: two classes A and B that refer to each other) and compiles cleanly, reduces unnecessary includes, and already appears in practice via iosfwd and in unit test libraries like doctest.

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" chapters (12)

1. 0:00Start
2. 0:05The Three Layers of Headers A Curious Discovery
3. 0:37fails to compile...
4. 1:38What's wrong with Attempt #2?
5. 1:48Let's step back...
6. 2:08Let's define dependencies of types, and member functions
7. 2:28There appears to be three layers
8. 2:52A Library Can Be Provided by Three Headers and One Source File
9. 3:54The Three Layers of a Library
10. 4:04Viktor Kirilov 'doctest' vs. 'catch' Compile Times
11. 4:25Library authors, refactor your
12. 4:52IOStreams Provides Forward Declarations

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