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
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()".
makeRange need not be a template but the code is a little
cleaner when
it is.
Would it not be even cleaner with less indentation, less ifs
and less
functions?:
Not always because not all complex range objects can be
assigned 'null'.
auto list = fail
? null // []
: someExpensiveOperation();
That does not work in the general case.
Use `typeof(someExpensiveOperation()).init` instead of `null` in
whatever general case you suggest.
BTW: The OP mentioned the notion of "fail fast". example_func
is not
fail fast.
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/
