Re: Function with defval returns error

Tom Lane wrote:
> This case *must* work:
> 
>     create function foo (f1 int)
>     create function foo (f1 int, f2 int = 42)
> 
>     select foo(10)
> 
> and it seems like just an arbitrary exception if you don't have a rule
> about preferring fewer defaults over more.

I tried out C++, and it rejects this case:

#include <iostream>
using namespace std;

int foo(int f1) { return 1; }
int foo(int f1, int f2 = 42) { return 2; }
int foo(int f1, int f2 = 42, int f3 = 43) { return 3; }

int main() {        cout << foo(10) << endl;
}

test.cpp: In function 'int main()':
test.cpp:9: error: call of overloaded 'foo(int)' is ambiguous
test.cpp:4: note: candidates are: int foo(int)
test.cpp:5: note:                 int foo(int, int)
test.cpp:6: note:                 int foo(int, int, int)


Interestingly, it complains about the calls, not the declarations, which 
is what I might have argued against.

So, I'd rather reject the foo(10) call.  The least-defaults rule doesn't 
strike me as very appealing.  If you are porting Oracle functions with 
40 arguments, it's very confusing and error-prone to say that the 
35-defaults variant will be called over the 37-default variant, more so 
if you extend this to name-based parameter lists where parameters and 
defaults can be in any order.  The whole thing is probably a mistake and 
should be rejected.