Comment by lmm | Hacker News Reader

Comment by lmm | Hacker News Reader

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> I just almost never have problems with this sort accidental conversion in practice.

95% of C++ programmers claim this, but C++ programs continue to be full of bugs, and they're usually exactly this kind of dumb bug.

> will be noticed by literally just running the code once.

Maybe. If what you're doing is "tricky mathematical algorithms", how would you even know if you were making these mistakes and not noticing them?

> the cost of visual noise of wrapper types, already higher just at the writing stage, then continues to be a cost every time you read the code. It's just not worth it for the very minor benefit it brings.

I find wrapper types are not a cost but a benefit for readability. They make it so much easier to see what's going on. Often you can read a function's prototype and immediately know what it does.

> Certainly, lifetime bugs are massively overshadowed by logic and algorithmic bugs.

Everyone claims this, but the best available research shows exactly the opposite, at least when it comes to security bugs (which in most domains - perhaps not yours - are vastly more costly): the most common bugs are still the really dumb ones, null pointer dereferences, array out of bounds, and double frees.

It’s the sociology of software development.

The guild of software developers has no real standards, no certification, no proven practices outside <book> and <what $company is doing> while continuing to depend on the whims of project managers, POs and so-caled technical leaders and others which can’t tell quality code from their own ass.

There’s usually no money in writing high-quality software and almost everything in a software development project conspires against quality. Languages like Rust are a desperate attempt at fixing that with technology.

I guess it works, in a way, but these kind of blog posts just show us how inept most programmers are and why the Rust band-aid was needed in the first place.

Maybe. But I wouldn't diss better languages, linters, and other tool inprovements. These systematically increase quality at very low cost. It boggles my mind that the whole industry is not falling over itself to continuously embrace better tools and technology.

The whole industry is, the C++ ecosystem is just not.

I don’t think that’s true. C++ just has a lot of baggage to deal with and people are doing the best they can with some ridiculous constraints. The sanitizers and things like clang-tidy, and better analysis in compilers seem to be really well received.

This. The industry is a hot-pot of gut feelings/seat of my pants mixed with true engineering and mathematical rigor.

It is all hit or miss. Everyone claims they do high-quality, critical software in public, while in private, they claim the opposite, that they are fast and break things, and programming is an art, not math.

And then you have venture capital firms now pushing "vibe coding."

Software development is likely the highest variance engineering space, sometimes and in some companies, not even being engineering, but "vibes."

It is interesting how this is going to progress forward. Are we going to have a situation like the Quebec Bridge [https://colterreed.com/the-failed-bridge-that-inspired-a-sim...]. The Crowdstrike incident taking down the whole airspace proved that is not enough. Market hacks in "decentralized exchanges," the same. Not sure where we are heading.

I guess we are waiting for some catastrophe that will have some venture capital liable for the vibe coding, and then we will have world wide regulation pushed on us.

Software developers no, but Software Engineering does, it is a professional title in many countries, where universities and engineers are only legally allowed to use such titles after being validated.

I really don't think this matters. It's the processes beyond physical engineering that make it better. I have seen the most highly accredited software devs write the worst code. I have seen self-taught devs deeply consider implication of the things they are writing and solve the problem simply. And it's not even the case that I can perceive a trend. Well except for PhDs, I have met only one PhD that I know can write actual good code.

I think if PhDs are bad at code it is because they ain't coding in a team 7.6 hours a day. It is not the PhDness rather than not being a coder. (Sone PhDs might code a lot as a hobby and be good).

You can also write a medical PhD without knowing how to do first aid on a snake bite.

My current project is a huge C++ physics sim written over 15+ years. The most common and difficult to diagnose bug I’ve found is unit conversation mistakes. We likely wouldn’t even find them if we didn’t have concrete data to compare against.

There are a few unit library in C++.

Type checking in compile time is do-able with templates, even better with constexpr.

The problem is, of course, each library have its own set of rules and they won't interop with each other.

I wrote such a type library myself, and it worked great. However we eventually realized it was the wrong answer because you so commonly want to display that thing and nobody wanted to write each widget to have a different api for each other the thousands of different types in my library.

The current system is a runtime system which has one type, and you set what the unit system is in the constructor. However it means adding a meter to a gallon is a runtime error.

Er... why would you need a different API for this? Why not just convert to unitless at the point where the number flows into the UI?

Or better yet, parametrize the UI library so that it can display any unit automatically. It could even pull the metadata (like the string for the unit) from the template, so that e.g. binding a kg<float> value to a label would automatically show as "42 kg" etc.

At the point where you convert to unitless you lose all the benefit of strong types. Which is a trade off maybe you can accept. One part of that trade off that you are adding the ability to convert to unitless and thus making it easy to use unitless where you shouldn't.

there are many different ways to implement unit systems. I know of 3 other attempts someone made on just our project to make units work before we settled on this one. There are trade offs and I don't mean to imply I have presented the correct answer for your problem. Only that because of many other reasons (not stated because of NDA) this is the best compromise for us. Your problem is different and you will need to find your own solution. There are lots of possible answers and each has a set of pros/cons. If your problems are simple than you can find an off the shelf answer, but if you need to do complex things you will need to consider what you really want.

I understand that there may be other requirements that dictate the design. It's just that the specific one that you gave originally - that of displaying the values - strikes me as something that shouldn't be difficult even when you have units reflected statically in the type system.

> At the point where you convert to unitless you lose all the benefit of strong types.

Right, but if you do that right before it actually gets displayed, then it shouldn't be a problem since all actual computations have been performed already? I mean, you also need to convert numbers to text to render them, so all the same arguments apply.

So e.g. in the "ideal" desktop app using MVVM, that would happen on the boundary between the model and the view-model.

> One part of that trade off that you are adding the ability to convert to unitless and thus making it easy to use unitless where you shouldn't.

But any typed unit-of-measure system inherently has such an ability if it tracks units properly for arithmetic operations - you just divide by 1 of the same unit to get a unitless value. E.g. in F#:

   let v = 10<m/s>      // in m/s
   let n = v / 1<m/s>   // unitless

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