Static assert at compile time

[hay]

Hi,

I've a project and it needs static asserts at compile time to check if string values are not left empty by the programmer. Is this possible in golang?

Thanks in advance

[robert engels]

I don’t think it is possible in any language - I think it is a very of the halting problem https://en.wikipedia.org/wiki/Halting_problem unless you are referring to checking a constant ?

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[Ian Denhardt]

It's a little unclear to me what exactly you're trying to check; giving
an example might make it easier to advise.

But in any case, Go doesn't have anything quite like static_assert in
C/C++. Depending on what you're trying to do, you could put a call to
panic in an init() function, which would at least catch the error on
program start.

Quoting hay (2018-10-27 18:07:08)

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[hay]

Hi robert, I'm looking for something C/C++ like static assertion to check few things at compile time.

Hi Ian, thanks for the reply. It is checking at init at the moment.

It is basically string or/and version checks. I'll give simple example. In C++ it will be something like this.

class Foo
{
    public: 
        static const string bar = "bar-version-01";
};

static_assert(Foo::bar != "bar-version-01", "Foo::bar version not same :(");

Above code will not compile if Foo::bar is different.

[David Collier-Brown]

In the special case of versioning, think about implementing "updaters" or "downdaters" on receipt of a versioned object/struct, as in https://leaflessca.wordpress.com/2017/02/12/dll-hell-and-avoiding-an-np-complete-problem/

For other uses, if you describe them here, we might be able to make a useful suggestion or two.

[T L]

If the strings values are constants, you can use this trick to assert they are not blank at compile time.

https://go101.org/article/tips.html#assert-at-compile-time

For example, for a constant string with name Version, you can assure it is not blank by using

var _ = map[bool]int{false: 0, Version != "": 1}

[Jan Mercl]

On Sun, Oct 28, 2018 at 2:16 AM T L <tapi...@gmail.com> wrote:

> For example, for a constant string with name Version, you can assure it is not blank by using
> 
> var _ = map[bool]int{false: 0, Version != "": 1}

Too complicated.

        const (

         Version = "v1.11"

        _          = 1 / len(Version)

        )

--

-j

[Lucio]

Too clever! :-)

Lucio.

[T L]

The var _ = map[bool]int{false: 0, contidion: 1} way is more general, it can be used to assert any conditions.

For OP's request, there are more ways, for example

type _ [len(Version)-1]int

But I admit the way shown by Jan Merci is the cleanest one. Cool!

[T L]

Another two things ways:

var _ = Version[:1]
var _ = Version[0]