Re: Keyword to avoid not null references

[Jesse Phillips]

On Saturday, 21 April 2012 at 22:18:02 UTC, Adam D. Ruppe wrote:
We can do not null in the library reasonably
well. I have a basic one in github:
https://github.com/D-Programming-Language/phobos/pull/477

I'm thinking those interested in not null will want something 
similar to the maybe type. As such checkNotNull shoud be more 
than throwing an exception. I have tried this, but it should get 
some constraints. Also wouldn't the new lambda syntax look nice 
with null here: null => unsafe(a)?

import std.stdio;

void main() {
    int* a;
    int i = 5;

    checkNull!(
              t => safe(t),
              () { unsafe(a); })
        (a);

    a = &i;

    checkNull!(
               t => safe(t))
        (a);

}

void checkNull(alias nn, alias n = () {}, T)(T a) {
    if(a !is null)
        nn(assumeNotNull(a));
    else
        n();
}


void safe(NotNull!(int*) i) {
    writeln(*i);
}

void unsafe(int* i) {
    writeln(i);
}