Question

I’m having problems trying to create the following lambda function:

const auto var x = [&y]() -> /*???*/ {
if (y == type1) {
  return some_type_1;
} else if (y == type2) {
  return some_type_2;
} else // ...

I know I cannot use auto as return type. But how can I do it in another way?

Thanks!

Answer 1

If some_type_1 and some_type_2 have a common type, write:

const auto var x = [&y]() -> typename std::common_type<
  decltype(some_type_1),
  decltype(some_type_2)>::type {
if (y == type1) {
  return some_type_1;
} else if (y == type2) {
  return some_type_2;
} else // ...

Equivalently, you can use a ternary expression:

const auto var x = [&y]() {
  (y == type1) ? some_type_1 :
  (y == type2) ? some_type_2 :
  ...;
}