On 1/1/26 9:01 AM, zhade wrote:
Hi, I am trying to fail-fast and need to return "something" that works
together with MapResult.
A method I used in the past is to put the entire range-generating code
inside a function that has a default argument (makeRange below):
import std;
auto someExpensiveOperation() {
return [ "hello" ];
}
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);
}
void main() {
example_func(true);
}
makeRange need not be a template but the code is a little cleaner when
it is.
That solution was a part of the following presentation (step 98/121 there):
https://youtu.be/dRORNQIB2wA?t=2628
Ali
