On 1/29/26 4:28 PM, kdevel wrote:
> On Thursday, 29 January 2026 at 20:44:17 UTC, Ali Çehreli wrote:
>> On 1/28/26 12:37 AM, kdevel wrote:
>>> On Tuesday, 27 January 2026 at 02:05:45 UTC, Ali Çehreli wrote:
> [...]
>>>> auto example_func(bool fail)
>>>> {
>>>> alias filterFunc = a => a != "expensive";
>>>> alias mapFunc = a => tuple!("value", "numLetters")(a, a.length);
>>>>
>>>> auto makeRange(R)(R r = typeof(someExpensiveOperation()).init) {
>>>> return r
>>>> .filter!filterFunc
>>>> .map!mapFunc;
>>>> }
>>>>
>>>> if (fail)
>>>> {
>>>> return makeRange();
>>>> }
>>>>
>>>> auto list = someExpensiveOperation();
>>>>
>>>> return makeRange(list);
>>>> }
>
> Your function is equivalent to
No because you don't apply filterFunc or mapFunc below.
> auto example_func (bool fail)
> {
> alias filterFunc = a => a != "expensive";
> alias mapFunc = a => tuple!("value", "numLetters")(a, a.length);
>
> auto list = fail
> ? typeof(someExpensiveOperation()).init
> : someExpensiveOperation();
>
> return list
> .filter!filterFunc
> .map!mapFunc;
> }
>
> but it has only two levels of indentation and no nested function
> (template). Alas it shares the duplication of "someExpensiveOperation()".
The problem is, one has to repeat filterFunc and mapFunc as well. And
that's why a nested function solves the repetition issue elegantly for me.
>> I must have misunderstood but it fails fast because it does nothing at
>> all before returning the empty result. (The OP's goal.)
>
> Maybe the OP favors a different definition of "fail fast" as the
> function under close scrutiny is not failing at all.
>
> FailFast also refers to some programming techniques that cause
> an exception to be thrown or other redirection of control to
> occur upon meeting certain conditions. [...]
>
> http://c2.com/
I must have read too much into the subject line: "empty" result. That's
why I'm reminded of this simple technique that I used in the past. I
assumed the OP was like me: the caller should not be bothered by
exceptions, rather an empty result should be returned.
Ali
