Null references

[Nick Treleaven]

On 21/08/2012 21:17, Nick Treleaven wrote:
>> I have an Option struct on my home computer that only allows access to
>> the held value if the error case is simultaneously handled:
>>
>> Option!int a = foo();
>>
>> int n = a.match!(
>>      (int x) => x,
>>      (None n) => 0 // or throw, or what have you.
>>      );

I've now implemented match, similar to the above:
https://github.com/ntrel/d-maybe/blob/master/maybe.d#L222

My match() always returns Maybe!T, because for pointers the lambdas 
could return null.

Taken from the unittest:

assert(match!(to!string, ()=>"<invalid>")(maybe(2)) == "2");
assert(match!(to!string, ()=>"<invalid>")(Maybe!int()) == "<invalid>");
assert(match!((x, y)=>text(x, y), {})(maybe(2), maybe(34)) == "234");
assert(match!((x, y)=>text(x, y), {})(Maybe!int(), maybe(34)) == null);
assert(match!((x, y)=>text(x, y), ()=>"none")(Maybe!int(), maybe(34)) == 
"none");

I'd be interested to see your Option code.

Nick