Operator overloading is an anti-feature and every language with it, would be better without it. Fight me.
Overloading gives user defined types the expressiveness of internal types. Like all features, of they are used badly (e.g when + is overloaded to an operation which can hardly be interpreted as addition) it makes things worse. But you can write bad code in any language, using any methodology.
The moment you have a language actually designed for numerics all these things vanish. One of Julias core design aspects is multiple dispatch, including operator overloading and it works extremely well there.
I also don't see the point for discoverability at all. The documentation will list the overloads and the non-overloaded calls are exactly as discoverable as the others.
plus(
mul(vec1, vec2),
mul(vec3, vec4))
https://downforeveryoneorjustme.com/eigen.tuxfamily.org?prot...
Of course, the compiler or an advanced IDE can know what your code means. If all your identifiers were random permutations of l and I: lIllI1lI, your IDE would not mind either, but the code would be horrific, don't you agree? The point of the OP is that overloaded operators (and functions) make it harder to reason about the code for a human that reads it. At least for some people. At the end, everything is "just" syntactic sugar, but it makes a significant difference.
Yes, the * operator can be ambiguous in the context of classic vector math (although that is just a matter of documentation), but not so much with SIMD vectors, audio vectors, etc.
Again:
a) vec4 = (vec1 - vec2) * 0.5 + vec3 * 0.3;
or
b) vec4 = plus(mul(minus(vec1, vec2), 0.5), mul(vec3, 0.3));
Which one is more readable? That's pretty much the perfect use case for operator overloading.
auto t = minus(vec1, vec2); mul_by(t, 0.5/0.3); add(t, vec3); mul_by(t, 0.3); v4 = std::move(t);
However, if the operands are small (e.g. 2/3/4 element vectors are very common), then "unnecessary copies" or move semantics don't come into play at all. These are value types and the compiler would boil them down to the same assembly as the code you post above. Many modern C++ codebases in scientific computing, rendering, or the game industry make use of vector classes with operator overloading, with no performance drawbacks whatsoever; however, code is much more readable, as it matches actual mathematical notation.
> Many modern C++ codebases in scientific computing, rendering, or the game industry make use of vector classes with operator overloading, with no performance drawbacks whatsoever
I guess these people are all not writing "serious code" :-p
Oh please, because you know exactly which kind of code I write? I'm pretty sure that with glm::vec3 the compiler can optimize this just fine. Also, "vec" could really be anything, it is just a placeholder.
That being said, if you need to break up your statements, you can do so with operators:
auto t = vec1 - vec2;
t *= 0.5/0.3;
t += vec3;
t *= 0.3;
And just for the record, I'm very glad Erin Catto decided to use operator overloading in his code. It made it much easier for me to read and understand what the code was doing as opposed to it being overly verbose and noisy.
[0]: https://github.com/erincatto/box2d/blob/main/src/collision/b...
Python's 'decimal' module uses overloaded operators so you can do things like:
from decimal import Decimal as D
tax_rate = D('0.0765')
subtotal = 0
for item in purchase:
subtotal += item.price * item.count # assume price is a Decimal
taxes = (subtotal * tax_rate).quantize(D('0.00'))
total = subtotal + taxes
>>> import decimal
>>> from decimal import localcontext, Decimal as D
>>> D(1) / D(8)
Decimal('0.125')
>>> with localcontext(prec=2):
... D(1) / D(8)
...
Decimal('0.12')
>>> with localcontext(prec=2, rounding=decimal.ROUND_CEILING):
... D(1) / D(8)
...
Decimal('0.13')
(1) If the first (left-most) digit to be removed is less than five, remove all the appropriate digits without changing the digits that remain. For example, 3.141593 rounded to the second decimal place is 3.14.
(2) If the first digit to be removed is greater than five, remove all the appropriate digits and increase the lowest-value remaining digit by one. For example, 3.141593 rounded to the fourth decimal place is 3.1416.
... (I've left out some lines)
(3) Divide the result in paragraph (a)(2) of this section by 5.5, and round
down to three decimal places to compute the fuel cost adjustment factor;
(4) Add the result in paragraph (a)(3) of this section to $1.91;
(5) Divide the result in paragraph (a)(4) of this section by 480;
(6) Round the result in paragraph (a)(5) of this section down to five decimal
places to compute the mileage rate.
This means simply doing all of the calculations in scaled bigints or as fractions won't really work.
Now of course, you could indeed handle all of this with prefix functions and with explicit context in the function call, but it's going to be more verbose, and obscure the calculation you want to do. I mean, it's not seriously worse. Compare:
with localcontext(prec=3, rounding=decimal.ROUND_DOWN):
line3 = line2 / D("5.5")
line4 = line3 + D("1.91")
line5 = line4 / 480
line6 = line5.quantize(D('.00001'), rounding=decimal.ROUND_DOWN)
line3 = decimal_div(line2, D("5.5"), prec=3, rounding=decimal.ROUND_DOWN)
line4 = decimal_add(line3, D("1.91"))
line5 = decimal_div(line4, 480)
line6 = decimal_quantize(line5, D('.00001'), rounding=decimal.ROUND_DOWN)
If overloaded parameters - "spooky action at a distance vibes" - also aren't allowed, then this becomes more rather more complicated.
can be overloaded! x and y could be any cobination of matrix, vector, or integer, float.
You're mixing up overloading (which is semantics) with syntax.
There's nothing that prevents me from implementing all of
plus(Int, Int)
plus(Int, Vec)
plus(Int, Mat)
plus(Vec, Vec)
plus(Vec, Mat)
plus(Mat, Mat)
You want every operation to have a distinctly named version for each other numeric type?
Maybe you can reduce some of those, but you can't really have interfaces without some overloading.
(plus
(mul vec1 vec2)
(mul vec3 vec4))
(+
(* vec1 vec2)
(* vec3 vec4))
In other places they monkey patch c++ defincies as a language.
And they are confusing and error prone.
Nobody is pretending we will get rid of any c++ syntax ever. So the discussion is about a hypothetical language syntax that fits C++ slot.
In that world C++ would have N x M matrices as native value types in the language (as fortran does) and those operators would be defined in the language spec for matrix types just as they are defined for standard number types at the moment.
And it would not have any operator overloading.
Any language with the level of industrial support C++ has had would have grown to prominence. C++ came abut a judicious time in history when "object orientation" was becoming the latest buzzword. And now we have ended up with gazillions of lines of C++ code.
It's a tragedy of our trade that two mongrels - C++ and Javascript - became to be among the most prominent in our trade.
Adding, javascript really inly has one industry its used in. Think it sais a bit about its versatility
That may be true for C++ (I'll take your word for it), but not for all programming languages in general. For example, in C# it's fairly common to overload == and != to implement value equality for reference types (classes).
Of course, you should really only do this for immutable classes that are mostly just records of plain old data. And C# 9 introduced record classes, which is a more convenient way of defining such classes. But record classes still overload these operators themselves, so you don't have to do it manually.
So, no overloading for decimal types? Nor fraction types?
I may be the oddball here, but I've used operator overloading on those types more than I have for vectors and arrays.
> And that's speaking as someone who once implemented a path class with a subtraction operator that would return the relative path between two absolute ones. I thought I was very clever.
Haha! It's ok. The temptation to be clever with operators is too strong, few can resist before getting burned (or more usually, burning others!) at least once.
Why the snark? The fact that you're free to make a bad choice does not imply that having a free choice must be bad. Obviously neither dot nor cross product should be *. It should be the Hadamard product or matrix multiplication. You can choose one convention for your code and be perfectly happy for it.
As a follow-up question: How do you feel about languages like Fortran and Matlab then? Is it actually a good thing that mathematics convenience features are relegated to a few math-oriented languages and kept away from all the others? (Or are the linear algebra types in these languages offensive as well?)
I'll pass.
Function names let you clarify that it is an outside product or inside product (e.g. there are often different types of adds, multiplies, divides), and I can not stand when someone maps cross product onto ^ (because you can both exponent and cross product some vectors, like quaternions, so why use exponent operator for cross?) or dot product onto something else that doesn't make any sense. Also operator overloading often doesn't make clear memory management, rather it relies on making new objects constantly, whereas with explicit functions, you can pass in an additional parameter that will take the result. Lastly, explicit functions allow you to pass additional information like how to handle various conditions, like non-invertible, divide by zeros, etc.
I find word-based functions more verbose but significant less error prone and also they are more performant (because of the full control over new object creation.) Operator overloading is only good for very simple code and even then people always push it too far so that I cannot understand it.
[1] 1997: https://github.com/bhouston/BezierCurveDemo1997/blob/master/..., 2001: C# math library: https://github.com/bhouston/ExoEngine3D/tree/master/Librarie..., 2013: a bunch of the core Three.js math library, 2023: https://github.com/bhouston/threeify/tree/master/packages/ma...
We have move semantics since C++11.
Alternatively, the main reason to use operators here is infix notation, so perhaps Haskell-like backticks.
Perhaps that idea falls apart once you realize you would need hundreds of symbols for just addition…
But what if those symbols were (automatically) imported and named at the beginning?
Perhaps it would be annoyingly inconsistent how in various files different symbols are used for the same operation…
I realize this is a minority opinion, but I don't want my editor to replace anything unless I've deliberately told it to.
For example my editor annotates auto with inferred types and function parameters with parameter names.
Just to be clear, I'm not being a smartass, just considering this as an option and wondering if the HN crowd has some thoughts on this.
That said, in my experience over the decades, operator overloading has been one of the primary causes of bugs that are very hard to pin down, so I have come to hate it. It hides far too much.
The cost/benefit ratio of operator overloading is generally unfavorable in practice, in my experience. Which is not to say it shouldn't be used when it actually clarifies things! But those situations tend to be fairly niche.
Interestingly, where I work right now, using operator overloading is specifically prohibited. So I'm confident that my dislike of the practice is not just a personal quirk.
As an example, early device models for circuit simulation were not designed to be numerically differentiable, leading to serious numerical artifacts and performance issues. Now we have courses dedicated to designing such models, and numerical analysis is used and emphasized throughout.
Is there anything today that you look at and think "yeah, they're gonna need to fix that at some point"?
sum({ mul(vec1, vec2), mul(vec3, vec4) })
OK.
Operator overloading is a useful feature that saves a bunch of time and makes code way more readable.
You can quibble whether operator<<() is a good idea on streams and perhaps C++ takes the concept too far with operator,() but the basic idea makes a lot of sense.
string("hello ") + string("world");
complexNumber2 * complexNumber2;
for (int i : std::views::iota(0, 6)
| std::views::filter(even)
| std::views::transform(square))
someSmartPtr->methodOnWrapperClass(); string("hello ").append("world");
complexNumber2.mult(complexNumber2);
// wtf is even going on with this one in your example? have these people never heard of method chaining?
for(int i : std::views::iota(0,6).filter(even).transform(square))
(*smartPtr)->methodOnWrapperClass();
3.times(2).plus(7)
(*smartPtr)->methodOnWrapperClass();
I understand the viewpoint that operator overload is syntactic sugar for things that can easily be done another way, I just disagree that costs outweigh the benefits.
Of course not. It makes sense for built-in types, as everyone reading the code can be assumed to know them.
> That is still using the overloaded SmartPtr<>::operator*() method.
Good catch ;)
> I just disagree that costs outweigh the benefits.
Yah, I think that's the disagreement. My feeling is there's a teeny, tiny handful of appropriate places for it (almost entirely math) and it opens up a pandora's box of terrible decisions that programmers clearly find irresistible.
3.times(2).plus(7)
Overloading operator| is a crude way to get the equivalent of extension methods without having to change the language.
"saves a bunch of time and makes code way more readable"
Not when everybody defines their own operators.
Note - we are discussing operator overloading, not operators as features in syntax. Operators at the syntax level make life a lot easier. But then everybody uses the exactly same operator semantics, not some weird per-project abstraction.
The lines of code you wrote as an example are not saving anyones time, except when writing it if you are a slow typist and lack a proper IDE support for C++. If typing speed is an issue, get a better IDE, don't write terser code.
The lines of code in the example save reader's time as they focus attention on the actual business logic.
Yes, this assumes that operator overloading follows some convention, but you need to follow conventions regardless to make readable code.
I think your argument is basically "people should not aggressively violate the implicit bonds of interfaces", which is true. But that goes for all interfaces, not just and not in particular those around operators.
We just have cases where it's common with operators because those are one of the few cases where we have lots of things that meet the interface and interact directly as opposed to hierarchically. The same kind of issue comes up with co/contravariant types and containers sometimes, but that's less often visible to end developers.
I don't like it in the example given
for (int i : std::views::iota(0, 6)
| std::views::filter(even)
| std::views::transform(square))
for (int i : std::views::iota(0, 6)
.filter(even)
.transform(square))
No deducing what `|` means, you are applying the filter then transform function against the view.
I think what people should advocate is full DSL capabilities with some unambiguous gate syntax so people know precisely that `foo * bar` is not using the host language syntax. Overloading operators is ambiguous and vastly incomplete (everyone is holding up matrix math as the shining example for the utility of operator overloading and you can't even express dot product notation in C++!)--it's a hack at best.
Except now you replaced + with a name that tells you just as much/little as + does. So you made your program verbose for the sake of verbosity.
https://en.wikipedia.org/wiki/Whitespace_(programming_langua...
The iostream bitshift overload was one of the first features of C++ that I learned to despise. I'm very happy that there's an alternative in the new version.
For my part, I've been persuaded that generic operators like that are a net win for math-heavy code, especially vector and matrix math. Sure, C++ goes too far, but there are middle grounds that don't.
For numeric value types mathematical operators are the only sane option.
For arbitrary classes - not so much.
A sane language in the slot of C++ in the language ecosystem would not have operator overloading. It would have matrix types defined in the language spec with mathematical operators operating on them.
Some folks prefer absl's flat_hash_map over std::unordered_map for a hash table, and it's not great that you need to choose or risk having both in a codebase, but it _is_ nice that you can have your preferred hash table and use operator[] whichever you decide.
Python also has operator overloading, and people seem to like that numpy can exist using it. And container types. Weirdly doesn't cause much consternation compared to C++ (maybe because the criticisms of the latter come from C programmers?)
I've occasionally missed overloading in JS/TS though.
This is unfortunately impossible (IMO). The problem is matrixes have multiple operations that don't translate nicely like complex numbers do. If you want to be consistent, you have to pick and choose What A * B means, under which contexts, and when is that illegal (or what should happen on an error).
For complex numbers, there's only one definition of A * B that matters and no failure cases.
I fear there's not clean way to do matrix operations that won't make some community really irritated for choosing "wrong". (Physics, engineering, science, etc.)
MyVecModule(v1 * v2 + v3)
Easy to read and explicit enough to know which functions is used.
https://dev.realworldocaml.org/files-modules-and-programs.ht...
The modern web is built on overloading the . operator (e.g. ORMs like Rails and Django). We will never see a Tier-1 ORM in Golang simply because it lacks it.
Gamedev, AI also benefits heavily from it.
Not true. It can be replaced with codegen.
See Ent (spun out of Facebook I believe)
Any advantages of Go (and there are many) are outweighed by the fact that you have to write and read 2x more code to be equally productive as Rails or Django.
That sounds like a good thing, having dealt with Hibernate in production. As a backend developer, I'm pretty happy with C++17 (and beyond), Go and Rust. All of them can be used in fairly explicit ways, which means debugging a problem is easy, and performance issues are right there on the page if any. I want less magic, not more.
Magic is magic until it becomes understood, then it is science.
While I don't want junior programmers wielding the dark magic of operator overloading, I trust that the engineers behind Django are using it reasonably.
Operators like +, -, /, *, etc have meanings independent of integers and floats and to not allow these meanings to be expressed is sad.
I've heard many programmers express this sentiment and what they actually are attempting to argue is that having overloads of these operators that do not respect the corresponding group, ring, or field laws is confusing. This I agree with. Operators should mainly follow the proper abstract semantics.
Allowing ANY operator to be overloaded was dumb, like C++ did, where you could do batshit crazy stuff like overloading unary & (addressof) or the comma operator (!), or stuff like the assignment operator (that actually opens a parenthesis about how copy/move semantics in C++ are a total hack that completely goes OT compared to this).
Sensible operator overloading makes a lot of sense, especially when combined with traits that clearly define what operations are supported and disallow arbitrary code to define new operators on existing types. Rust does precisely that, and IMHO it works great and provides a much nicer experience than Java's verbose mess of method chaining.
The Google C++ style guide has a very nice overview. There are only two pros listed, and large number of cons. And this document is old by Internet (dog) years -- at least 10 years.
Ref: https://google.github.io/styleguide/cppguide.html#Operator_O...
Built in operators don't always map 1-1 to CPU instructions so don't appeal to that authority. There are still plenty of CPUs -- old and new -- without multiplication, division, or floating point support.
vec3 foo{1, 2, 3};
vec3 bar{2, 0, -2};
auto baz = foo + bar; // {3, 2, 1}
Considering there are like 3 different types of matrix multiplication operations, I don't think it's obvious at all. Feels like you should either use a language with complete support for implementing custom DSLs (that can express the whole domain naturally) or eschew ambiguous operator overloading altogether (gaining consistency and quality at the expense of a few keystrokes).
DSLs just push the complexity away from the language into someone else’s problem in a way that has much higher sum complexity. You’re making authors of numerical libraries second-class citizens by doing so. For some languages that’s probably not a bad choice (Go is one example where I don’t feel the language is targeted at such use cases).
Also, the lack of a standard interface for things like addition, multiplication, etc. means that mathematical code becomes less composable between different libraries. Unless everyone standardizes on the same DSL, but I find this an unlikely proposition, given that DSLs are far more opinionated than mere operator overloads.
Yes. And it tortures me every time.
I religiously avoid string concatenation in Python for this very reason. It's not that "+" necessarily means addition; it's that it always means a commutative operation (to somebody who has learned some algebra). String concatenation is notoriously non-commutative, thus it is extremely disturbing to write it using a visibly commutative operator. Any other operator except "+" would be better. For example, a space, or a product, or a hyphen. Whatever. But please, not a commutative operator. It breaks my brain parser.
When it comes to languages that let you mix strings and numbers, Lua has it right. + always adds, and accepts numbers and strings that can cleanly convert to numbers. .. always concatenates, and accepts numbers and strings.
I love me some operator overloading. I love / for filesystem separators, I love | for piping things. I don't like << and >> so much but that's just because of too many years of writing them everywhere.
1. Operator overloading
2. Operator desugaring (e.g. __subscript__(), which substitutes the intrinsic function for basic types, but can also be defined for user defined types)
3. Writing templates with weird adaptors for primitive types.
Given that its design goal was to embed C, there were already operators that worked with various and mixed types. Adding (+.), etc., would have been unacceptable to the users. So, I think in general, for this language, it was good but, unfortunately, iostream made people think you should overload the behavioral expectation, too.
If you wanted to use an abstraction over non primitive types for such things you would use a normal function.
The fact that it makes syntax "nicer" for user defined types is at best subjective and at worst an anti-pattern because it leads to bad compiled code and confused programmers. Function calls are unambiguous and follow the same rules as other function calls, while operator overloading does not.
Bjarne has given a couple of interviews on the matter.
[1] https://en.cppreference.com/w/cpp/io/cout
The others are more sus but you can make a bad API out of anything.
Rewriting (say) a load of calculations as a tree of sum pow exp etc. is just a huge burden - a codebase I work on has a formula that takes up about 6 lines for example, outputted by mathematica: total pain to to translate to function calls.
Yahhhh but there's something about operator overloading that is like catnip to clever programmers. Ah ha, file paths have slashes, and the divide operator is a slash! Clearly I should use the divide operator to append paths segments together! I'm so clever! Ah ha, << looks kinda like an arrow I guess, so we can use it to, uh, pass data between objects, I guess. I'm so clever...?
It's irresistible. We have abused it and we must give it up for the good of all.
I quite like that one but I'd be willing to give it up for the hobgoblin of my little mind.
Most programming languages use infix notation for mathematical operations but polish notation for function calls. This creates an inconsistency. In languages, like LISP, that entirely use polish notation the inconsistency does not exist.
One could argue that if a programming language has this inconsistency, then one should at least try to be consistent with one's notation, i.e. for mathematical operations use infix notation (operator overloading).
Like with many things in C++, its another grenade, but when used appropriately is pretty great
In Scala, infix operators and methods are the same thing.
a + b
a.+(b)
a.map(b)
a map b
https://github.com/manifold-systems/manifold/tree/master/man...
Lunch, behind the cafeteria. Closed fists allowed, nothing below the belt.
OK, come to my glass labyrinth where you don't know which of a dozen images of me are the real instance.
You will soon appreciate obfuscation techniques.