On Thursday, 16 February 2017 at 00:08:12 UTC, Walter Bright
wrote:
On 2/15/2017 12:31 PM, Jonathan M Davis via Digitalmars-d wrote:
It's one of those features that I was surprised when you
couldn't do it.
It was an oversight. We just never thought of it.
What do you think about generalizing this feature to allow
introducing template value parameters without default value, i.e.:
// Note: `beg` and `end` have no default value
auto bounded
(auto beg, auto end, auto onErrPolicy = Enforce("Value out of
range"), T)
(T value)
{
return Bounded!(beg, end, Policy)(value);
}
struct Enforce
{ this(string) { /* */ } }
int tmp;
readf("%s", &x);
enum policy = Enforce("User age must be between 18 and 150");
auto userAge = bounded!(18, 150, policy)(tmp);
"Declaring non-type template arguments with auto" is also coming
to C++17:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0127r1.html
BTW, shouldn't we use `enum`, instead of `auto`, since everywhere
else `enum` means guaranteed to be computed at compile-time
whereas `auto` means the opposite?
