Go 1.2 Release Candidate 1 released | Hacker News Reader

Go 1.2 Release Candidate 1 released

tip.golang.org

76 pointsbabawere39 comments

I am so happy they decided to include comparison operators in text/template and html/template [1]. It drove me nuts to have to write comparison functions and call them from within the template. Yes, it kept some logic out of the template but in my opinion it added an unnecessary layer of indirection.

[1]: http://tip.golang.org/doc/go1.2#text_template

> go/build: support including C++ code with cgo (CL 8248043).

As someone who spent all of yesterday trying to figure out the best workaround for the lack of this functionality, I'm very happy to see this change.

I really want to like Go, but I'm having a hard time believing that they don't have a plan for generics. I've read the FAQs about go+generics, but do we have any better idea of when generics might make an appearance? Not being able to write a generic "map" function in a modern language seems very strange to me.

edit: there's something "map"-ish here: https://code.google.com/p/go/source/browse/src/pkg/exp/itera...

> I really want to like Go, but I'm having a hard time believing that they don't have a plan for generics. I've read the FAQs about go+generics, but do we have any better idea of when generics might make an appearance?

As a language feature: not likely any sooner than Go 2.0, given everything that's been said on the issue, though I suppose if a way could be found to do generics that doesn't explode compilation time and doesn't involve syntax changes that would break any existing Go 1.x code, it might happen in a later 1.x release. Wouldn't hold my breath.

Via a preprocessor? Its already a thing: https://github.com/droundy/gotgo

http://golang.org/doc/faq : "Generics are convenient but they come at a cost in complexity in the type system and run-time. We haven't yet found a design that gives value proportionate to the complexity, although we continue to think about it. Meanwhile, Go's built-in maps and slices, plus the ability to use the empty interface to construct containers (with explicit unboxing) mean in many cases it is possible to write code that does what generics would enable, if less smoothly."

One of Go's goals is a certain level of simplicity. The above point seems to state that generics don't fit that goal, but they are not precluded from a future version.

I take this to mean that since no language has every feature that anyone could possibly want, if generics are a requirement for your work, then Go does not fit the requirements.

Some potentially relevant material here - http://commandcenter.blogspot.de/2012/06/less-is-exponential... :

"Early in the rollout of Go I was told by someone that he could not imagine working in a language without generic types. As I have reported elsewhere, I found that an odd remark."

> I really want to like Go

Why? 4 years on seems a long enough time to come to term with what Go is.

Has anyone tried the new scheduler?

Does this still block forever?

package main

import "time"

func main() { go func(){ for {} }() time.Sleep(time.Millisecond) }

while they have added some preemption to the scheduler, go is still generally cooperative multitasking. I believe function calls are also schedule points now. If you have a cpu-intensive loop you want to yield from at certain points, stick a runtime.GoSched in there. Having a busy-loop in your code is going to mess things up, and is usually a bug anyway.

> Having a busy-loop in your code is going to mess things up, and is usually a bug anyway.

A busy loop is a sufficient way to emulate a heavy computation (e.g. applying effects to image files or compressing data) when it's not optimized out.

That will still block forever. If you include a function call in the loop though, it won't.

Ok, I just tried it. It still does.

This is great: "Finally, an HTTP server will now serve HEAD requests transparently, without the need for special casing in handler code. While serving a HEAD request, writes to a Handler's ResponseWriter are absorbed by the Server and the client receives an empty body as required by the HTTP specification."

Been waiting for this forever...

It would be nice to see performance benchmark between 1.1 and 1.2

So run your Go programs with 1.1 and with 1.2 and tell us if there's a difference.

Whenever they fix the tremendous issue of errors being ignored by default, give me a call.

Whenever that issues does become "tremendous" (seriously?), give me a call...

Could you expand on this? I'm not sure I follow.

I think what GP is getting at that if you call a function with one return value, you can ignore it by not assigning anything to the result of the function.

http://play.golang.org/p/9J46QRHul1

They presumably would like to force you to use the return value if it is of type error.

Ah, got it. I thought it was way more sinister than that.

On a side note, does any programming languages force you to use the return value of every function call?

OCaml gives you a warning ("this function should return unit") if you don't use the result of each function call, unless that function returns unit (void). You can suppress it with the "ignore" function or with "let _ = some_function() in …"

I would like to implement this feature in Rust as well, as it would have saved me hours of debugging a couple of times.

> OCaml gives you a warning ("this function should return unit") if you don't use the result of each function call, unless that function returns unit (void). You can suppress it with the "ignore" function or with "let _ = some_function() in …"

GHC can also do so optionally (with -fwarn-unused-do-bind) (and I'm unsure there even is a way to ignore return values outside of do blocks)

Go forces you to either assign the return value to a variable and then use that variable, or pretend it doesn't exist at all. I think they were trying to get rid of the middle "assign it to a variable, deal with it later" case, to encourage people to write error-handling code there and then, but I've found that instead it pushes me towards completely ignoring error codes, then because there's no "unused variable 'errorCode'" warning, I forget to go back and robustify the code :(

I probably /should/ get into the habit of writing error-handling code at the same time as writing the main-path code, but for someone who's just started learning the language and just wants to see what works, I find it really frustrating >_<

You soon get used to the pattern:

  blah, err := foo(...)
    if err != nil {
      return nil, err
  }

and it's sister:

  blah, err := foo(wibble)
    if err != nil {
      return nil, errors.New("foo error with blah due to: " + wibble)
  }

After a while I got to like passing errors carefully back up the call stack , cleaning them up, rewriting them and making them more useful.

My Go programs have far better (more detailed & relevant) error messages than any of my other code.

You might like:

   _, err := somethingThatFails(arg)
   if err != nil {
      return fmt.Errorf("failed with arg=%v, %v", arg, err)
   }

Now the use for this is not obvious from this toy example, but having a `printf`-like function that produces error is great to return errors with more context.

The difference from your example is that the info in `err` is not lost when passed up.

And you might like:

  if _, err := somethingThatFails(arg); err != nil {
    return fmt.Errorf("failed with arg=%v, %v", arg, err)
  }

In that case I was ignoring the returned value for the sake of the example, otherwise you lose the declaration when it's in a `if`.

I do like that.

(I just picked (and cleaned up) the first piece of simple error code that I thought would be easy to use.)

> You soon get used to the pattern:

Yes, we all know how good humans are at work which no computer could ever do such as repetitive output of pointless generic boilerplate.

My point is that translating an error from one call to the previous is neither generic nor pointless.

An exception and line-number (and a call-stack dump) is great for a developer, but a good textual error message is needed for a real user.

> My point is that translating an error from one call to the previous is neither generic nor pointless.

The first pattern does not do that. The second one is still mostly pointless generic boilerplate:

    blah, err := 
    if err != nil {
        return nil, errors.New()
    }

is all boilerplate, only two parts are not: the call itself and the error message.

> An exception and line-number (and a call-stack dump) is great for a developer, but a good textual error message is needed for a real user.

1. having exceptions doesn't preclude handling them and writing user-readable error messages

2. exceptions are not the only alternative to C-style error handling

Can you tell me about the other alternatives? I'm actually interested in this and I have searched for alternatives at least to see how they look.

I'm sure I don't know most of them (e.g. I have no idea how Prolog does error handling), but I know of:

* the Haskell/ML statically typed approach, error possibility is type-encoded through an Option or Either type; even in cases where it is possible to implicitly ignore return values[0] the compiler will warn or error; the standard library provides high-level operations to pipeline results (build a pipeline of operations which will only transform non-erroneous results, and will let errorneous ones go through)

* the Erlang dynamically typed approach which makes use of tagged pattern matching to make value assertions trivial. It is not shorter than the Go version when fully handling things, but assertion can be used to fault processes during development or when in-process user-visible reporting is irrelevant (fairly common in erlang) yet remain easy to find and replace with more involved handling if needs be

[0] because haskell strives for purity, ignoring return values in non-monadic code makes very little sense and I'm not sure it's possible at all short of unsafe* functions. It is possible in monadic code (e.g. do blocks)

I agree with sambeau on this one. I have come to like the go way of doing things: it's extremely simple, doesn't take much thought, and after a little while is very easy to read.

... then because there's no "unused variable 'errorCode'" warning, I forget to go back and robustify the code

Well, you can always assign the error code to '_', and then just grep for those later. Or you can take the 10 seconds and just add the code to return the error as sambeau suggests.

If it's a fairly big function, or a common way of dealing with errors in a package you can always define a func (nested or not):

  func foo() error {
    handleErr = func(err error) bool {
      if err != nil {
         log.Println(err)
         // do other stuff
         return true
      }
      return false
    }
    err := bar()
    if handleErr(err) { return err }
  }

It's nice and concise.

He probably wants exceptions.

Sounds like the oft-repeated cry of the C-based language dev in regards to a lack of exceptions in Go.

The blog and comments here have summed this debate up nicely: http://uberpython.wordpress.com/2012/09/23/why-im-not-leavin...

Linked in that article (http://benchmarksgame.alioth.debian.org/u64q/code-used-time-...) is a comparison of conciseness and performance. Interesintgly the FP languages are put in a right-more / less-concise column than Go, C, C++ (unless I am reading it wrong).

Since the verbosity of error handling in Go is part of the debate here, are not FP languages often more concise? Is "concise-ness" really an issue?

I don't think this should be the default behavior since you would end up writing a lot of boilerplate

  _ = myFunc()

code. But it would be nice if the vet tool had a (optional) feature to warn you about ignored return values.

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