On Friday, 10 May 2024 at 01:00:09 UTC, Andy Valencia wrote:
On Friday, 10 May 2024 at 00:40:01 UTC, Meta wrote:
Yes. The reason for this is that it avoids having to
essentially do the same check twice. If `in` returned a bool
instead of a pointer, after checking for whether the element
exists (which requires searching for the element in the
associative array), you'd then have to actually *get* it from
the array, which would require searching again. Returning a
pointer to the element if it exists (or `null` if it doesn't)
cuts this down to 1 operation.
Looking at Programming in D section 28.5, I'm guessing that
pointer versus null is treated as the appropriate boolean value
when consumed by an "if" test. So that example is getting a
pointer to a string, or null, but the example looks exactly as
the same as if it had directly gotten a bool.
Yes, we say that a type has "truthiness" if it can be used in a
condition (`while`, `if`, `assert`, etc).
For a pointer, `null` is considered "false", whereas any other
value is considered "true". So you can use statements like
`if(key in aa)` to test for membership. A very nice idiom is to
check if a key is in an associative array, and if so, use the
value that it maps to:
```d
if(auto v = key in aa) {
// use *v as the value here
}
```
You can change your code to `return (e in this.members) !is null;`
-Steve
