This program now compiles and runs under the Epoch trunk:

//
// SUMTYPEFUNCTION.EPOCH
//
// Basic test of functions operating on sum types
//

type test : integer | string



sumfunc : integer param
{
assert(param == 42)
}

sumfunc : string param
{
assert(param == "bletch")
}


entrypoint :
{
test foo = 42
test bar = "bletch"

sumfunc(foo)
sumfunc(bar)

print("Pass")
}


This paves the way for things like optional (nullable) types, and other coolness.

Typing is entirely static at the moment; if you initialize a sum type with type A, it will transparently convert the variable to type A during compilation, and the variable will always be of that type. Since the language already has overload support, decomposing a sum typed variable into its "real" type is trivial, as shown above.

The one missing feature is pass-through support (i.e. where I take a sum type and pass it through a function without inspecting it, which I can't do because I haven't settled on its type statically). I'll probably hack on that next.

For now, though, I'm pretty happy with how easy it was to get sum types working as well as they are. With the addition of a special "nothing" type and some generic-programming goodies, it should be possible to do pretty amazing stuff with the Epoch type system real soon now.


Woot.