Summary Digital Education & Knowledge Sharing Acknowledges
This is a technical blog post on C++ compiler optimization (devirtualization and static polymorphism), published openly without paywalls. The content engages minimally with human rights, but supports Article 19 (free expression), Article 26 (education), and Article 27 (scientific progress) through its open publication model and contribution to technical knowledge commons. The site demonstrates accessibility-conscious design that supports broader educational access.
Nice overview, it misses other kinds of dispatch though.
With concepts, templates and compile time execution, there is no need for CRTP, and in addition it can cover for better error messages regarding what methods to dispatch to.
One of the papers I had bookmarked when toying with my own language design was someone that had worked out how to make interfaces as fast or faster than vtables by using perfect hashing and using the vtable as a hash table instead of a list.
You can also, when inlining a polymorphic call, put a conditional block in that bounces back to full dispatch if the call occasionally doesn’t match the common case. The problem with polymorphic inlining though is that it quickly resembles the exact sort of code we delete and replace with polymorphic dispatch:
if (typeof arg1 == “string”) {
} else if typeof arg1 === …) {
} else if {
} else if {
} else {
}
> Under the hood, a virtual table (vtable) is created for each class, and a pointer (vptr) to the vtable is added to each instance.
Coming from C++ I assumed this was the only way but Rust has an interesting approach where the single objects do not pay any cost because virtual dispatch is handled by fat pointers. So you carry around the `vptr` in fat pointers (`&dyn MyTrait`) only when needed, not in every instance.
I've been thinking through what features I'd want in a language if I were designing one myself, and one of my desires is to have exhaustive matches on enums (which could be made of any primitive type) and sum types. The ability to generate perfect hashes at compile time was one of the things that falls out nicely from that
> using the vtable as a hash table instead of a list.
Could you explain this a bit more? The word "list" makes me think you might be thinking that virtual method lookup iterates over each element of the vtable, doing comparisons until it finds a match -- but I'm certain that this is not how virtual method invocation works in C++. The vtable is constructed at compile time and is already the simplest possible "perfect hashtable": a short, dense array with each virtual method mapping to a function pointer at a statically known index.
There have been type-erasure libraries in c++ for a longish time that allow choosing inline vtables and inline storage. It's definitely been a widely talked about technique for at least 10 years (I see talks about Dyno from 2017).
Editorial Channel
What the content says
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Article 26Education
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Article protects education and human development. Content provides technical knowledge that contributes to education and skill development in computer programming and software engineering.
FW Ratio: 60%
Observable Facts
Blog post presents detailed technical instruction on C++ compiler optimization techniques.
Content is written at moderate technical level, assuming some programming knowledge.
Responsive typography and layout observable in CSS declarations support readability.
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Technical education content contributes to human development and skill acquisition rights.
Accessibility-conscious design supports broader educational access across devices and contexts.
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Article 19Freedom of Expression
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Article protects freedom of opinion and expression. Content is a technical blog post presenting programming knowledge without editorial restrictions, censorship, or editorial control visible.
FW Ratio: 60%
Observable Facts
Blog post is publicly accessible without subscription or authentication barriers.
Technical article presents programming concepts in straightforward expository style.
Content appears unmoderated by external editorial authority.
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Open publication of technical knowledge supports the right to share and receive information freely.
Absence of visible editorial filtering suggests author autonomy in expression.
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Article 27Cultural Participation
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Article protects participation in cultural and scientific progress. Content is a technical article contributing to scientific and technical knowledge commons in computer science.
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Technical knowledge is presented for public benefit and understanding.
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Freely shared technical knowledge contributes to collective scientific progress.
Open publication enables broader participation in and benefit from technical advancement.
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PreamblePreamble
Content is a technical article about C++ programming; no engagement with UDHR preamble concepts (dignity, freedom, justice, peace).
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Article 1Freedom, Equality, Brotherhood
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Article 2Non-Discrimination
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Article 6Legal Personhood
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Article 12Privacy
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Article 21Political Participation
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Article 29Duties to Community
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Article 30No Destruction of Rights
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Article 26
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Article 19 Article 27
Content appears freely accessible without subscription or paywall; open publication model supports information dissemination.
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Article 19Freedom of Expression
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Content is published freely without paywalls or access restrictions; open publication model supports information dissemination. Domain DCP indicates free access model with +0.08 modifier.
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Article 27Cultural Participation
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Free, open publication model allows broad participation in and benefit from technical knowledge advancement. DCP +0.08 modifier for access model supports this.
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Article 26Education
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Site demonstrates accessibility design (responsive layout, typography optimization); DCP modifier of +0.05 for accessibility features supports educational access.
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PreamblePreamble
No structural mechanisms observable that relate to preamble themes.
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Article 1Freedom, Equality, Brotherhood
No discriminatory or inclusive structural design signals.
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Article 2Non-Discrimination
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Article 3Life, Liberty, Security
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Article 4No Slavery
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Article 5No Torture
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Article 6Legal Personhood
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Article 7Equality Before Law
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Article 8Right to Remedy
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Article 9No Arbitrary Detention
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Article 10Fair Hearing
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Article 11Presumption of Innocence
No relevant signals.
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Article 12Privacy
No privacy-invasive or privacy-protective mechanisms observable.