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Comment by lloydatkinson | Hacker News Reader

So it appears this follows the terrible C++ "naming things with the wrong name on purpose" trend, with the biggest example being naming a variable length array (a list, collection, etc) `std:vector` even though Vector was already a well known word with a very different meaning.

The word/type they wanted for this was the Unit type: https://en.wikipedia.org/wiki/Unit_type and in that list it even states the `std:monotype` is a Unit.

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I'd argue that unit would be just as cryptic as monostate, if you don't know what either is.

Like, if we assume someone looking at code with `std::unit`, what might they think this is? If one is not aware of its use in ML or similar, it could just as easily be assumed that it could be something to do with units like meters or kilograms or whatnot. After all, the C++ standard library is vast so it wouldn't necessarily be all that far-fetched.

Then the only question would be to ask why it would be default-constructible. At which point you'd have to read the docs for the type anyway.

It’s called “unit” because it is a unit of the operation of multiplication / constructing a tuple (up to a unique isomorphism): for any type 't the tuple types unit * 't and 't * unit are isomorphic to 't. When you don’t have that as a fundamental operation in your type system, like ML does, then it could be confusing.

sure, but I would be surprised if a significant fraction of programmers knew that. When we hear the word "unit", that's not the first definition that comes to mind.

There is indeed a units library [0] aiming for standardisation in C++29.

[0] https://github.com/mpusz/mp-units

> I'd argue that unit would be just as cryptic as monostate, if you don't know what either is.

And if my grandmother had wheels she'd be a bicycle. Of course if there wasn't a standard name for this concept that had been used in the industry for 50+ years (and in theoretical work for over 100) then it wouldn't make any difference what name you used for it. But given that there is a standard name for this concept that has been used in the industry for 50+ years, making up a different name is pretty unfortunate.

I mean, the industry is composed by much, much, much more C++ than ML programmers

My guess is the maintainers of C++ keep making it more and more awful in an attempt to force people to more sane languages.

But to their dismay the crazier it gets, the more some people dig in and embrace it even more.

/sarcasm. I think.

It's not sarcasm. The maintainers have completely lost the plot.

Even Herb Sutter agrees(I think, in his heart, even if he doesn't come out directly and say it), which is why he is working on cppfront

Functor is one of the worst offenders IMO. In C++ lingo, it simply means "callable object".

In C++ lingo they are called function objects or callables, not functor. You might stumble on code here and there that suffix a class name with Functor but it's not that common.

Many blog posts and Stackoverflow questions about C++ cal them functors. Boost of all things uses the term in its definitions: https://www.boost.org/doc/libs/1_60_0/doc/html/function/refe...

It's common enough that articles have been written against this usage: https://web.archive.org/web/20170224220253/http://jackieokay...

So this usage of functor may never have been "official", but it's widespread in the community.

I would say it was widespread, but it's now fallen out of favor. Alexandrescu got the name wrong 25 years ago† and that got embedded into early boost, but by the time that blog post was written I feel like I'd mostly stopped seeing it being used by C++ experts.

† I don't know if the original mistake was his, but he certainly did a lot to spread it.

cppreference.com uses the term functor in numerous places for recent C++ features including things in C++26 such as reflection:

https://en.cppreference.com/w/cpp/experimental/reflect

https://en.cppreference.com/w/cpp/utility/variant/visit2

https://en.cppreference.com/w/cpp/experimental/parallelism

Visual Studio's official documentation uses the term functor as of 2021:

https://learn.microsoft.com/en-us/cpp/standard-library/funct...

A simple Google search shows no shortage of recent websites and documents including fairly authoritative references using the term functor to describe a type that overloads operator ().

Heck even the author of this article, Raymond Chen, uses the term functor as recently as 2020 to describe such a construct:

https://devblogs.microsoft.com/oldnewthing/20200513-00/?p=10...

Is Raymond Chen not a C++ expert?

> In C++ lingo they are called function objects or callables, not functor.

The word "functor" has a long and glorious history in C++. Try entering "C++ Andrei Alexandrescu functors" into your internet search engine of choice. For bonus points, try "c++ Scott Meyers functor" as well.

The creator of C++ uses the term functor in the book "The C++ Programming Language" to describe any object that overloads operator ().

It's not like anyone has a monopoly on the term: https://en.wikipedia.org/wiki/Functor_(disambiguation)

The C++ usage was introduced by Jim Coplien in his 1992 book as a succinct name for an architectural pattern in C++: https://archive.org/details/advancedcbsprogr00copl/page/166/...

Coming from other languages I noticed this about C++ as well. I can't give examples right now but I recall multiple times being like: "Oh that is just a weird name for $KnownComputingConcept".

Reactive style programming also takes the Unit as the value to act upon when the value and the type does not actually matter and only the action does.

https://stackoverflow.com/questions/54336641/is-there-any-re...

Consider ML appropriating the term tensor...

The term "vector" represents an ordered collection of elements(ex 3-dim vector is [x,y,z]). A list is flat out incorrect because it is used to refer to linked list(std::list), and a collection means a group of objects and that can be anything like a map, set, etc so it's too generic.

Before C++ popularized the term, other programming languages and libraries had already used "vector" to describe similar data structures. For example, Common Lisp has a vector type that represents a one-dimensional array.

Stepanov introduced the term in C++ and he fully acknowledges that it was a bad name and that he regrets it. If he could redo it, he would have renamed it array or array_list.

Interview with him acknowledging this:

https://www.youtube.com/watch?v=etZgaSjzqlU

It doesn't help that mathematics and physics have their own overlapping but unequal definitions of "vector".

As does Biology.

And computing has interrupt vectors as well.

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