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I'm still a bit of a novice, could someone elaborate on what he means by operator overloading being "problem creating?" I thought that was one of the main, 'cor

I'm still a bit of a novice, could someone elaborate on what he means by operator overloading being "problem creating?" I thought that was one of the main, 'core' concepts of OOP. Inheritance, and polymorphism. How would you make something like a GUI without being able to specialize classes by overriding certain methods? Have I misunderstood his point?

paraboul 14y ago
Opertor overloading is really horrible. By reading the code "foo + bar" you can't know what is really doing internally. He is talking about operator (+-*=[]&) overloading. Not method overloading.
- gurkendoktor 14y ago
  And how do you know what add(foo, bar) does internally?
  - azylman 14y ago
    add(foo, bar) isn't any clearer than foo + bar, but usually an overloaded operator doesn't correspond to "add". For example, in Javascript: "Hello" + " " + "World!". What the operator there is doing is concatenating the strings, so if you had a method to do it you wouldn't call it add - you'd call it concat.
    - numeromancer 14y ago
      But then you lose the information that both ((usually modular) arithmetic, and strings with concatenation, et al.) are monoids, and have a similar structure, and creating generic functions which might use that symmetry becomes more difficult.
    - rat87 14y ago
      In python you can overload + and a lot of other numeric operators by implementing certain methods __add__ for +, see others here: http://docs.python.org/reference/datamodel.html#emulating-numeric-types http://docs.python.org/reference/datamodel.html#emulating-nu... In ruby you can implement certain numerical methods including + In smalltalk + is a binary method, you can give your methods all sort of symbol names. Same with Scala I think.
    - gurkendoktor 14y ago
      > For example, in Javascript: "Hello" + " " + "World!". What the operator there is doing is concatenating the strings Hmm, are we talking about (user defined) operator overloading as a language feature, or about overloaded operators? For example, I hate that 1/2 and 1.0/2 are different things in most languages, but I haven't heard anyone call this operator overloading in the context of C.
  - SeanDav 14y ago
    You are missing the point. You might not know exactly what add() does internally but "+" only gives you a 1 character description, requiring you to know, or assume behaviour of the terms being added. By using a function name instead, you have far more opportunity to describe more clearly what actually is going to happen, requiring less assumption which as we know is the mother of ....
- pcwalton 14y ago
  I wish I could agree, but experience has shown that not having operator overloading makes (a) operating polymorphically over different number types and (b) creating new number types (decimals, bigints, etc.) really awkward. The former is much of the reason we had to add it to Rust. We have matrices that can operate over any numeric type T that implements the basic operations (so we can write matrix math once and have it work on 32-bit floats and 64-bit floats; this is important for speed vs. precision for browsers vs. scientific computing), but we couldn't put an addition operator in the Num interface, so we had to make "add", "sub", etc. methods. The result made our matrix math operations nigh-unreadable.
  - bjz 14y ago
    How did you solve the problem in your matrix libraries of overloading a single operator multiple times? I was trying to make rudimentary, game-oriented linear algebra library in rust along the lines of glm. I immediately ran into the problem of not being able to implement "mat4 * float->mat4", "mat4 * vec4->vec4" and "mat4 * mat4->mat4" overloads at once. The alternative was only to go with "mult_float", "mult_vec4" and "mult_mat4", but as you say this leads to "nigh-unreadable" code. It might seem petty, but whilst I understand rust avoiding overloading functions entirely (due to type problems and code obfuscation), it was enough to turn me off entirely, in this case sending back to D. Bear in mind this is not to say Rust is a bad language - there's plenty to like about it. ;)
    - LinaLauneBaer 14y ago
      I don't know rust but rust seems very much like C++. Did you have a look at the Eigen library (C++)? http://eigen.tuxfamily.org/dox/TutorialMatrixClass.html http://eigen.tuxfamily.org/dox/TutorialMatrixClass.html I have never worked with this library but it seems to me that they have not the problems you described. Maybe having a look at it brings up some new ideas...
      - bjz 14y ago
        Although on superficial level it shares the AGOL/C-style syntax, Rust is a very different language from C++. Some things are possible or easier in Rust as opposed to C++ and vice-versa. Copying directly from a C++ library would be difficult, and wouldn't take advantage of Rust's unique strengths.
- rat87 14y ago
  "foo + bar" looks like a string
Lewisham 14y ago
His point is that, if you aren't familiar with the code, operator overloading can be difficult to read. It gives objects the appearance of being native types, and it is sometimes not entirely clear what the result of the overload might be. What does "dog + cat" equal? In an extreme example, if you are crazy enough, it might make sense to have animal + animal = baby animal. You need to temper that example down to something closer to reality :) I personally like overloading, but I think it's probably too easy to abuse, and I can see how it would cause problems with a team size larger than 5. As far as I can see, whenever the Go team encountered a language feature that could possibly be abused, they always deferred to leaving it out. Whether that is good or bad I'm not sure we will know until we have years of experience with it.
- luriel 14y ago
  > As far as I can see, whenever the Go team encountered a language feature that could possibly be abused, they always deferred to leaving it out. All features can be abused. The Go philosophy is more to leave out features that obscure the meaning and understanding of code (what is also known as "magic"). Also part of the Go philosophy is to not include any feature unless it is clear that its benefits are greater than its costs, and which might interact in unpredictable ways with other existing features. In other words, the default is to leave things out, rather than to include them, the opposite of a kitchen sink approach.
- goostavos 14y ago
  Ah, that makes sense. Really good explanation. Thanks!
- WalterBright 14y ago
  I think the poster child for operator overloading abuse is iostreams overloading << and >>. However, operator overloading is very much needed for when creating user defined types that have arithmetic properties, such as bigint, or matrix. As for the confusion about whether + means "add" or "concatenate", that is unresolvable. The D programming language deals with it by introducing the ~ binary operator to mean "concatenate". No more problems. Although in D one can overload operators to mean any crazy thing one wants to, the consensus in the community is to eschew non-arithmetic use in the same manner that the C community has condemned: #define BEGIN { #define END }
mseebach 14y ago
The argument is roughly that it is, in fact, not very useful, while opening up a vast array of misuses - especially in the domain of being all too clever. What does "+" mean on a list and an object? Add, probably. But what if it's two lists? Union? Or add the second list as the last element to the first? Named functions "add" and "union" aren't any less readable and loads more descriptive. The only situation you positively need operator overloading is when doing arithmetic, and you should do that using the built in types. This, of course, sucks when the built in types are inadequate, and you e.g. want to use a arbitrary precision library such as BigDecimal in Java. This, of course, is an opinion, and I'm not shy to admit it's been shaped by being burned by Lift, the Scala web framework which makes heavy use of symbolic function names which makes it incredibly difficult to talk about or search for answers online.
- Lewisham 14y ago
  Of course, Go itself is completely unsearchable, so you always have to search for Golang, which means that thee mut be hundreds of pages that get missed.
  - mseepgood 14y ago
    And "C" or "D" are searchable? Or "Java" (island, coffee) or "C#" (musical scale)? Or "Basic" (fundamental)? Or "Python" (snake) or "Ruby" (gemstone)? Or "Lisp" (speech impediment)? Or "Pascal" (French mathematician, SI unit and general given name)? Or "Smalltalk" (informal conversation)? Or "Logo" (emblem)? Or "Lua" (Portuguese word for moon)? ...
    - lalmalang 14y ago
      In my humble opinion, in the vast majority of cases, yes. Because " C ", " D ", " C# " should be easier for search engines to disambiguate (at least working with Lucene, it is, and I imagine Google etc are similar-ish). As for Java, Python the context in the page likely to point to its intended audience (and it helps they have been around for ages etc). Otoh, " go " is likely to be used in a lot of literature, including other programming related texts. Try searching for something with clojure, and then try go -- the quality of results is usually substantially different, and my unsubstantiated hunch is that not all of it has to do with lack of go-related content. Seems to be getting better though..
mseepgood 14y ago
Operator overloading has nothing to do with OOP. In go you get polymorphism via interfaces and you can share implementation via embedding. http://golang.org/doc/effective_go.html#embedding http://golang.org/doc/effective_go.html#embedding
robharper 14y ago
Yes, I think you misunderstood. You are thinking of overriding methods, which is very important. Operator overloading is where you redefine the behavior of a "+" symbol, for example.
- rat87 14y ago
  In a number of oo languages + is a method(smalltalk, ruby, python)(possibly using some sort of special casing of addition for integers/floats to speed up the common cases)/
skybrian 14y ago
I haven't seen a GUI written in Go yet, but the basic idea is that you don't customize via inheritance; you do it in a different way. For example, in many UI libraries, you can create a function and ask a widget to call you when you receive an event; the widget will have methods like: addClickHandler(myFunction) Any customization you could do with inheritance could be done with a callback function instead, provided that the object has the hook you want. In Go, there is also an "interface" which is basically a set of methods.
- LinaLauneBaer 14y ago
  That is more or less how UIs using Cocoa/Cocoa Touch are working from a developer standpoint of view. Most standard views/controls have a delegate property which is informed about certain things happening or asked when an important decision has to be made. This works extremely well and by implementing a delegate you get around the problems related to subclassing UI controls/views. Now that Objective-C/C has blocks Apple began to replace (or add) block based "callbacks" which makes life easier in most cases.

paraboul 14y ago

Opertor overloading is really horrible. By reading the code "foo + bar" you can't know what is really doing internally. He is talking about operator (+-*=[]&) overloading. Not method overloading.

gurkendoktor 14y ago
And how do you know what add(foo, bar) does internally?
- azylman 14y ago
  add(foo, bar) isn't any clearer than foo + bar, but usually an overloaded operator doesn't correspond to "add". For example, in Javascript: "Hello" + " " + "World!". What the operator there is doing is concatenating the strings, so if you had a method to do it you wouldn't call it add - you'd call it concat.
  - numeromancer 14y ago
    But then you lose the information that both ((usually modular) arithmetic, and strings with concatenation, et al.) are monoids, and have a similar structure, and creating generic functions which might use that symmetry becomes more difficult.
  - rat87 14y ago
    In python you can overload + and a lot of other numeric operators by implementing certain methods __add__ for +, see others here: http://docs.python.org/reference/datamodel.html#emulating-numeric-types http://docs.python.org/reference/datamodel.html#emulating-nu... In ruby you can implement certain numerical methods including + In smalltalk + is a binary method, you can give your methods all sort of symbol names. Same with Scala I think.
  - gurkendoktor 14y ago
    > For example, in Javascript: "Hello" + " " + "World!". What the operator there is doing is concatenating the strings Hmm, are we talking about (user defined) operator overloading as a language feature, or about overloaded operators? For example, I hate that 1/2 and 1.0/2 are different things in most languages, but I haven't heard anyone call this operator overloading in the context of C.
- SeanDav 14y ago
  You are missing the point. You might not know exactly what add() does internally but "+" only gives you a 1 character description, requiring you to know, or assume behaviour of the terms being added. By using a function name instead, you have far more opportunity to describe more clearly what actually is going to happen, requiring less assumption which as we know is the mother of ....
pcwalton 14y ago
I wish I could agree, but experience has shown that not having operator overloading makes (a) operating polymorphically over different number types and (b) creating new number types (decimals, bigints, etc.) really awkward. The former is much of the reason we had to add it to Rust. We have matrices that can operate over any numeric type T that implements the basic operations (so we can write matrix math once and have it work on 32-bit floats and 64-bit floats; this is important for speed vs. precision for browsers vs. scientific computing), but we couldn't put an addition operator in the Num interface, so we had to make "add", "sub", etc. methods. The result made our matrix math operations nigh-unreadable.
- bjz 14y ago
  How did you solve the problem in your matrix libraries of overloading a single operator multiple times? I was trying to make rudimentary, game-oriented linear algebra library in rust along the lines of glm. I immediately ran into the problem of not being able to implement "mat4 * float->mat4", "mat4 * vec4->vec4" and "mat4 * mat4->mat4" overloads at once. The alternative was only to go with "mult_float", "mult_vec4" and "mult_mat4", but as you say this leads to "nigh-unreadable" code. It might seem petty, but whilst I understand rust avoiding overloading functions entirely (due to type problems and code obfuscation), it was enough to turn me off entirely, in this case sending back to D. Bear in mind this is not to say Rust is a bad language - there's plenty to like about it. ;)
  - LinaLauneBaer 14y ago
    I don't know rust but rust seems very much like C++. Did you have a look at the Eigen library (C++)? http://eigen.tuxfamily.org/dox/TutorialMatrixClass.html http://eigen.tuxfamily.org/dox/TutorialMatrixClass.html I have never worked with this library but it seems to me that they have not the problems you described. Maybe having a look at it brings up some new ideas...
    - bjz 14y ago
      Although on superficial level it shares the AGOL/C-style syntax, Rust is a very different language from C++. Some things are possible or easier in Rust as opposed to C++ and vice-versa. Copying directly from a C++ library would be difficult, and wouldn't take advantage of Rust's unique strengths.
rat87 14y ago
"foo + bar" looks like a string

Lewisham 14y ago

His point is that, if you aren't familiar with the code, operator overloading can be difficult to read. It gives objects the appearance of being native types, and it is sometimes not entirely clear what the result of the overload might be. What does "dog + cat" equal? In an extreme example, if you are crazy enough, it might make sense to have animal + animal = baby animal. You need to temper that example down to something closer to reality :) I personally like overloading, but I think it's probably too easy to abuse, and I can see how it would cause problems with a team size larger than 5. As far as I can see, whenever the Go team encountered a language feature that could possibly be abused, they always deferred to leaving it out. Whether that is good or bad I'm not sure we will know until we have years of experience with it.

luriel 14y ago
> As far as I can see, whenever the Go team encountered a language feature that could possibly be abused, they always deferred to leaving it out. All features can be abused. The Go philosophy is more to leave out features that obscure the meaning and understanding of code (what is also known as "magic"). Also part of the Go philosophy is to not include any feature unless it is clear that its benefits are greater than its costs, and which might interact in unpredictable ways with other existing features. In other words, the default is to leave things out, rather than to include them, the opposite of a kitchen sink approach.
goostavos 14y ago
Ah, that makes sense. Really good explanation. Thanks!
WalterBright 14y ago
I think the poster child for operator overloading abuse is iostreams overloading << and >>. However, operator overloading is very much needed for when creating user defined types that have arithmetic properties, such as bigint, or matrix. As for the confusion about whether + means "add" or "concatenate", that is unresolvable. The D programming language deals with it by introducing the ~ binary operator to mean "concatenate". No more problems. Although in D one can overload operators to mean any crazy thing one wants to, the consensus in the community is to eschew non-arithmetic use in the same manner that the C community has condemned: #define BEGIN { #define END }

mseebach 14y ago

The argument is roughly that it is, in fact, not very useful, while opening up a vast array of misuses - especially in the domain of being all too clever. What does "+" mean on a list and an object? Add, probably. But what if it's two lists? Union? Or add the second list as the last element to the first? Named functions "add" and "union" aren't any less readable and loads more descriptive. The only situation you positively need operator overloading is when doing arithmetic, and you should do that using the built in types. This, of course, sucks when the built in types are inadequate, and you e.g. want to use a arbitrary precision library such as BigDecimal in Java. This, of course, is an opinion, and I'm not shy to admit it's been shaped by being burned by Lift, the Scala web framework which makes heavy use of symbolic function names which makes it incredibly difficult to talk about or search for answers online.

Lewisham 14y ago
Of course, Go itself is completely unsearchable, so you always have to search for Golang, which means that thee mut be hundreds of pages that get missed.
- mseepgood 14y ago
  And "C" or "D" are searchable? Or "Java" (island, coffee) or "C#" (musical scale)? Or "Basic" (fundamental)? Or "Python" (snake) or "Ruby" (gemstone)? Or "Lisp" (speech impediment)? Or "Pascal" (French mathematician, SI unit and general given name)? Or "Smalltalk" (informal conversation)? Or "Logo" (emblem)? Or "Lua" (Portuguese word for moon)? ...
  - lalmalang 14y ago
    In my humble opinion, in the vast majority of cases, yes. Because " C ", " D ", " C# " should be easier for search engines to disambiguate (at least working with Lucene, it is, and I imagine Google etc are similar-ish). As for Java, Python the context in the page likely to point to its intended audience (and it helps they have been around for ages etc). Otoh, " go " is likely to be used in a lot of literature, including other programming related texts. Try searching for something with clojure, and then try go -- the quality of results is usually substantially different, and my unsubstantiated hunch is that not all of it has to do with lack of go-related content. Seems to be getting better though..

mseepgood 14y ago

Operator overloading has nothing to do with OOP. In go you get polymorphism via interfaces and you can share implementation via embedding. http://golang.org/doc/effective_go.html#embedding http://golang.org/doc/effective_go.html#embedding

robharper 14y ago

Yes, I think you misunderstood. You are thinking of overriding methods, which is very important. Operator overloading is where you redefine the behavior of a "+" symbol, for example.

rat87 14y ago
In a number of oo languages + is a method(smalltalk, ruby, python)(possibly using some sort of special casing of addition for integers/floats to speed up the common cases)/

skybrian 14y ago

I haven't seen a GUI written in Go yet, but the basic idea is that you don't customize via inheritance; you do it in a different way. For example, in many UI libraries, you can create a function and ask a widget to call you when you receive an event; the widget will have methods like: addClickHandler(myFunction) Any customization you could do with inheritance could be done with a callback function instead, provided that the object has the hook you want. In Go, there is also an "interface" which is basically a set of methods.

LinaLauneBaer 14y ago
That is more or less how UIs using Cocoa/Cocoa Touch are working from a developer standpoint of view. Most standard views/controls have a delegate property which is informed about certain things happening or asked when an important decision has to be made. This works extremely well and by implementing a delegate you get around the problems related to subclassing UI controls/views. Now that Objective-C/C has blocks Apple began to replace (or add) block based "callbacks" which makes life easier in most cases.