NullReferenceException
NN
painful.
Today you can do the following:
def a = ["a", null, "b"];
And then if you want to print all values you have to do the following:
a.Filter(i => i != null).Iter(Console.WriteLine);
Pay attention to Filter method.
Why do you need it ? Because you can get null! Very very sad.
What can be a solution ?
Prevent using null values.
def a = ["a", null, "b"]; // Compilation Error
And if user wants null values , he must admit it.
def? a = ["a", null, "b"];
def a : list[CanBeNull[string]] = ["a", null, "b"];
The type CanBeNull[T] can be converted to T.
From the point of .Net.
T where T : class ==> Reference type with compile time restriction.
Can be used only in Nemerle code.
T where T : struct ==> T
CanBeNull[T] where T : class ==> Regular reference type. Can be used
for connecting code.
CanBeNull[T] where T : struct ==> Nullable<T>
Possible syntax for CanBeNull[T] - T?
class A
{
private x : string;
private y : string?;
F() : void
{
// if (x == null) // No need
Console.WriteLine(x);
if (y != null) // Can be null
Console.WriteLine(y);
}
}
What do you say about it ?
VladD2
What about changing Nemerle type system to make NRE problems less
painful.
It's big task. I think, we implement it in Nemerle 2.0.
NN
Do you think it is possible and/or useful ?
It will be nice to make a list for possible Nemerle 2.0 features.
On Mar 21, 6:10 pm, VladD2 <v...@rsdn.ru> wrote:
> Hi
>
> 2010/3/21 NN <nn1436...@gmail.com>
VladD2
It is more theoretical question now.
Do you think it is possible and/or useful ?
It is possible and useful.