for example, long ago, i was looking at the source for some of the go libraries and couldn't understand why they had cut+paste code. when i asked on stackoverflow the unaminous answer was "because go doesn't support generics". you can see the discussion here - http://stackoverflow.com/questions/6645329/why-does-the-go-i...
BUT if you read that thread, and the discussion under the first answer, you'll see that there is an apparently reasonable solution without generics. that seemed like an obvious approach to me (coming, i guess, more from python and fp), but one that wasn't obvious to anyone answering (coming, i guess, more from java and c).
i have no evidence that this is a general problem, but it surprised me at the time. ever since i have been suspicious of people complaining about the lack of generics (disclaimer: i don't use go myself - when i looked at it i thought that it was clear improvement on c/c++/java, but could have been even better if they had been more open to ideas from fp - http://acooke.org/cute/GoRocksHow0.html ; in other words, i'd be happy to use it at work instead of c (current project), but if i can choose myself i'm more likely to go with a more functional approach).
i think the general conclusion from this thread is that generics would be useful because, at the moment, if you want top performance, you need to have type unsafe code in critical loops.
that sounds quite reasonable to me...
...so maybe i am just an arrogant bastard that doesn't think much of fellow programmers. but i suspect that most people, when they complain about generics are not making that argument. they're simply complaining because it's not what they are used to.
as i say, i may be wrong. i may be a horrible man. if people want to convert/improve me i suggest they start making comments that are a bit more nuanced than "i miss generics".
Such as the familiarity of java developers who had to wait for a decade to get generics? The familiarity of C developers where void*? Or the familiarity of Python developers where "whatever"?
This claim doesn't check out.
Common container data structures are one example. You can't write, say, a generic binary search tree in Go, unless you wrap all your data in an interface. While possible, this means you have to downcast all over the place.
The built-in map, while useful, is limited in how far it goes.
Maybe I'm just spoiled by the STL and the Java collections libraries.
map :: (a -> b) -> [a] -> [b]
Essential: no.
Map/Filter introduce several new semantic concepts to a language. I think they were avoided for simplicity's sake and the fact you can achieve the same result with a for loop, even if it is slightly less concise.
No they don't. If you already have first-class functions (Go does) and some sort of sequence type (Go does), you have map/filter. There's no new semantic concepts.
The only added simplicity here is for the compiler writers, not the end users.
for i, n := range numbers { numbers[i] = n * n }
Sorry, but I do not see a difference in the order of assembly language vs. high-level language.
Higher order functions are really useful for splitting apart navigation of a data structure and the processing of the data contained within it.
Given that you can use purely higher order functions for control flow, I wouldn't say one is more essential than the other.
a) With a more complex type (I don't see how this would affect one more than the other)
Functional would be:
foos = map(foos, func(f Foo) Foo { return Foo{f.A * f.A, f.B * f.B} })
Iterative is:
for i, f := range foos { foos[i] = Foo{f.A * f.A, f.B * f.B} }
b) Composing various operations. Composing filter + map:
Functional would be:
x := filter(map(numbers, func(n int) int { return n * n }), func(n int) bool { return n % 2 == 0 })
Iterative is:
x := make([]int, 0); for _, n := range numbers { sq := n * n; if sq % 2 == 0 { x = append(x, sq) } }
c) Swapping the container type is just a matter of swapping "_, n := range numbers".
It does because the discussion is about generics. The fact that you're writing out types for one and not the other makes your comparisons a bit disingenuous, though I understand if Go isn't very good at functional programming.
b) Composing various operations. Composing filter + map:
As you keep building them up the imperative style will have more code overhead and less efficiency.
> c) Swapping the container type is just a matter of swapping "_, n := range numbers".
This isn't true since the functional one could easily swap out to use an infinite data source whereas the imperative will be constrained to the arrays you're already using.
b) No, it will not be less efficient. It's all done within one loop, in-place. You can compose everything inside the body of the loop. A functional language would do the same if it's intelligent.
c) You can easily create an infinite data source in Go with the generator pattern:
numbers := make(chan int); go func() { for i := 0; ; i++ { numbers <- i } }()
for n := range numbers {...}
Yes, I should have said type inference obviously. I can't think of a decent functional language that doesn't have type inference though.
> No, it will not be less efficient. It's all done within one loop, in-place. You can compose everything inside the body of the loop. A functional language would do the same if it's intelligent.
If it's all done in one loop then it isn't composing. It's writing custom code every time you need to do something.
> You can easily create an infinite data source in Go with the generator pattern:
That's nice, you only need to change all of your code to do so. The functional version doesn't have that problem.
Please note that if your comment thread starts getting squished against the right side of the page like this, it might be time to move the conversation off of HN.
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It could be a linked list that links back to it's own head. It could be a network stream, or a series of events from an input device. The program doesn't have to care.
It's a different way of approaching things. I'd say that golang was stream-based rather than functional or imperative.
https://github.com/tcard/functional
I can't say I've actually needed to use map or filter. You can, much as people did for the last 30 years and still do with C, quite happily do this sort of stuff with a for loop...
I suspect this is why a lot of people who've jumped on the Golang bandwagon come from Python & Ruby: they're already used to no compile-time type safety, so they're not missing anything. For people who like type systems and have a style of programming that relies upon them, Go doesn't give them the tools they need to be productive.
In Steve Yegge's terms: C++ is a pretty software-conservative update to C (it even has backwards-compatible syntax). Meanwhile, Go is a pretty software-liberal update (slightly to the right of Python). G simply does not support a software-conservative programming style. Consequently, Go's adoption has mostly come from software-liberal communities.
The mapper can take care of almost everything using a few conventions and reflection, and for anything where those conventions don't cover it you plug in a little custom code (inherit from Mapper<,> or use composition).
Not sure how you’d handle that sort of case in Go without generics?
Implementing a top-class GUI toolkit that is not just a binding to an existing one would be at least half a decade of work. And when it's done all GUIs will be rendered by web views anyway. The web is the presentation layer of the future. Classic desktop widget sets like QtGui or Swing will fit nowhere, because all the consumer operating systems like iOS, OS X, Android and Windows 8+ will have highly custom user interface paradigms, which won't be mappable to each other by some cross-platform thing.
This. Go makes it fantastically simple to go from 0-to-web-server.
There were a few projects I wanted to write in Go, but avoided because of needing a GUI.
Then I remembered: I can just bolt a web-page onto my app, and I get a GUI for free [assuming knowledge of HTML/CSS/JS].
Even better: that GUI will work on any computer with a modern web-browser, including my phones. If you stick to standards, it should even be a reasonably consistent UX across the newer browsers.
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While I would still _like_ to see a good UI toolkit for Go, I really think it's less of a necessity than most would have you believe.
I'm playing with the idea of a Cairo/Postscript type library with X, Win32, Quartz backends in Golang which would be a good foundation for such a thing.
I have got precisely nowhere apart from trying to connect to an X server unsuccessfully though :)
I find programming to be easy (relatively). I find interfaces to be almost insurmountably difficult. That's the only reason I stick exclusively to command-line programs.
Odd. Here's my 5 min explanation of how GUI programming works:
You have a bunch of objects that are responsible for generating events and painting themselves to the screen. They exist in hierarchies. You have objects that coordinate the transitions between different display states by swapping out different hierarchies (view FSMs, really.) You communicate with your domain backend thread/process through some kind of command channel. When your domain models change, they publish some events that go back through that channel to notify your display hierarchies so they can update themselves. Everything is async and through message passing.
The difficulties can be in a) setting up your hierarchy of display objects and b) getting your event routing / updating to happen in a clean way. Oh yea, and c) handling partially-complete domain models in the ui ;)
Cocoa/CocoaTouch and Flex are both quite nice environments for gui programming. I haven't used MFC, winforms or xaml/winrt..
Of everything you describe, I think the area I struggled most with was:
>getting your event routing / updating to happen in a __clean__ way.
I was a naive and young programmer, so I'll withhold any criticisms towards WinForms, but the event routing was a _mess_ by the end of that project.
That's a personality type (mine too). Probably best to bite the bullet with HTML/CSS. I think non-web interface builders are a thing of the past. Which is too bad, because CSS is a monster to master.
Developers need tools too so we shouldn't just abandon non-web technologies.
No. [Edit: I'm talking about apps that use webviews make a native-looking app. Web apps don't qualify.]
Colloquy represents the chatroom text as a stream of XML, which it uses XSLT themes to translate into HTML, which is displayed in a WebView. I'm sure Adium does something similar.
"Using HTML/CSS/JS as the new GUI medium" doesn't limit itself to just running stuff in a traditional browser. I was under the assumption that we were talking about making HTML/CSS/JS the new GUI layer, even for native apps.
http://go-lang.cat-v.org/library-bindings
Check out the "GUIs and Widget Toolkits" section.
Add some sort of decent generics and you're really close.
A top-class GUI toolkit would be good too.