Re: [OT] Some neat ideas from the Kotlin language

[Kagamin via Digitalmars-d]

On Tuesday, 23 February 2016 at 22:03:32 UTC, Xinok wrote:

On Tuesday, 23 February 2016 at 19:43:43 UTC, rsw0x wrote:

...

How does this differ from the example I gave where the branch is only taken if the pointer is non-null?

D doesn't prevent you from dereferencing a null pointer whereas these scenarios should be impossible in Kotlin as well as Rust. Case and point, this code compiles without issue but crashes at runtime:

    int* foo()
    {
        return null;
    }

    void main()
    {
        if(int* ptr = new int)
        {
            ptr = foo();  // Whoops...
            *ptr = 35;    // Crash
        }
    }

In D, pointers and reference types can spontaneously become null under almost any context. That's the difference.

The idea is to match non-null pointers, this is how you do it:

    int* foo()
    {
        return null;
    }

    void main()
    {
        if(int* ptr = foo())
        {
            *ptr = 35;    // no crash
        }
    }