Hi! On Feb 15, 2010, at 1:07 AM, Terence Parr wrote:
Ok, thanks Kay (and George in a private thread). it sounds to me like we only really need to specify the AST type (which can default to object when we don't care...hmm...can Java do that?) and token type. token type is fine as an interface; no point in parameterizing, unless there's some optimization that the compiler will find when we use more concrete types but it seems to work okay now
There's no optimization at all, no. All it does is to add type safety, type erasure makes generic types look the same at runtime (or to use my favorite obfuscation from the manuals: Parameterized types are not covariant :)). If we don't need them, that's fine. Alternatively one could use a bounded wildcard type for the payload, e.g. <? extends Token>, but I'm not sure we really need to over plain Token. We'll see, it's easier to check it out once the code is working anyway.
I don't think we need to default to Object at all, since someone needs to specify the ASTLabelType anyway (hetero trees might still need casts in actions, though, but not for the generated and runtime code, since we won't care about their special methods/fields at that level, only that the corresponding tree adaptor can handle the node types). Again, maybe using ASTLabelType = <? extends BaseTree> could work as a default, as long as we only call methods declared in BaseTree on them (and let the tree adaptor handle the rest). I'd have to see actual code before deciding though, generics overwhelm my brain and I'm severely under-caffeinated :)
cheers, -k -- Kay Röpke
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