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0 pointsncmncm4y ago0 comments

This pattern goes back to pre-Version-7 UNIX kernels, with only minor syntactic updates. That it long predates OO demonstrates it is not OO. That does not make it any less effective, or less useful.

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adrian_b4y ago

It does not predate OO.

The first OO language, SIMULA-67 became public knowledge before the start of even the PDP-7 UNIX, which is extremely unlikely to have used such a pattern, which probably appeared only when UNIX was rewritten in C, starting in 1973.

Even Smalltalk-72 predated the C-version of UNIX.

However, it is likely that this pattern was chosen in UNIX independently of the previous OO languages.

pjmlp4y ago

Also what many usually forget, C++ was also born on the same building as UNIX.

Hence why C++ got so fast adopted across UNIXes and C compiler vendors on other platforms.

ncmncmOP4y ago

That was not the reason.

But it was the reason that C, as standardized, adopted several C++ innovations first.

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mst4y ago

To a great extent, the difference between "a data structure plus a dispatch table" and "an object" is primarily in how you squint.

It's certainly a form of polymorphism.

rurban4y ago

It's a measurable difference. OO in C++ must use double indirect vtable method calls, whilst this OO in C uses only one indirection. It's measurably faster. Objects are a bit larger though, cloning is a bit more expensive, but method calls are much faster and much easier to cache.

aaaaaaaaaaab4y ago

I think you're misinterpreting GP's code. It is a vtable, hence the static const. There would be a pointer in each struct "instance" to this static vtable, thus the same double indirection would occcur as in C++.

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jcelerier4y ago

> That it long predates OO demonstrates it is not OO.

This does not make any sense. People did not wait until someone gave a name to the rule-of-three to use it, and that does not make these uses any less rule-of-three than the ones that occured post-naming.

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