Return type deduction in recursive function

Following code compiles :

auto foo(int i) {
  if( i == 1 )
    return i;
    return foo(i-1)+i ; 

While following doesn't, c++1y

auto foo(int i) {
  return (i == 1) ? i : foo(i-1)+i ;  

Why can't compiler deduce the return type in second case ? Am I missing something over here ?

I know there's a sequence point after (i == 1) in second scenario, but that shouldn't be affecting compilation, right ?


The first works because of this rule, of the latest draft

Once a return statement has been seen in a function, however, the return type deduced from that statement can be used in the rest of the function, including in other return statements.

So the return type is deduced as int from the first return statement; the second is just checked to make sure that it also gives int, assuming that the recursive call does.

The second doesn't compile because the type of the expression depends on the return type; so the type can't be deduced.

A recursive function can have an auto return type only if it has a non-recursive return statement before the recursive call. See Return type deduction for normal functions.

Need Your Help

Biometric finger scanner deserializing template from database C#

c# serialization biometrics

good day to all I just need some help. I was wondering if my code is correct so please guide if it is not. I have a Digital Personal Biometric Model 4500 using DPFP .NET (C#) SDK I was able to