Re: Another purity question

[Timon Gehr]

On 01/14/2014 09:21 PM, David Nadlinger wrote:

On Tuesday, 14 January 2014 at 19:50:10 UTC, bearophile wrote:

But is it possible for D to see that bar function as pure?

In the general case, no:

---
auto foo(const int[] a) {
     int bar() {
         return a[0];
     }
     return &bar;
}

void main() {
     int[3] a;
     auto dg = foo(a[]);
     assert(dg() == 0);
     a[0] = 1;
     assert(dg() == 1);
}
---

David

int delegate()pure foo(const int[] a)pure{
    struct S{
        const int[] a;
        int bar()pure{
            return a[0];
        }
    }
    auto s=S(a);
    return &s.bar;
}

void main() {
    int[3] a;
    auto dg = foo(a[]);
    assert(dg() == 0);
    a[0] = 1;
    assert(dg() == 1);
}