On 2015-10-26 12:40, Edmund Smith wrote:
You could also emulate constant matching using default parameters
(albeit with the restriction that they must be after any
non-default/constant parameters), since the defaults form part of the
function's type. I tried making something like this earlier this summer
and it'd check that a given value was first equal to the default
parameter and match if so, or match if there was no default parameter
but the types matched.
e.g.
//template ma(tch/g)ic
unittest
{
Algebraic!(string, int, double, MyStruct) v = 5;
string s = v.match!(
(string s = "") => "Empty string!",
(string s) => s,
(int i = 7) => "Lucky number 7",
(int i = 0) => "Nil",
(int i) => i.to!string,
(double d) => d.to!string,
(MyStruct m = MyStruct(15)) => "Special MyStruct value",
(MyStruct m) => m.name, //
() => "ooer");
writeln(s);
}
It's a bit ugly overloading language features like this, but it makes
the syntax a little prettier.
Why not just use a value as an extra argument:
v.match!(
7, (int i) => "Lucky number 7"
);
Scala's Option is really nice on the other hand since you can/should pattern
match).
I thought it was preferred to use the higher order functions like "map"
and "filter".
--
/Jacob Carlborg
