53 lines
1.4 KiB
Text
53 lines
1.4 KiB
Text
1. in parser we need.. type unification?
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2. or perhaps just need to introduce type variables.
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3. we can't resolve type for a recursive pair of functions until we've seen both of them..
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tho we could require letrec
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def foo = lambda (n : i64) { let (n == 0) then 1 else n * foo(n - 1); };
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strategy:
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----------
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while parsing def, instead of creating DefineExpr with nullptr TypeDescr:
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a. create DefineExpr with TypeVariable.
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(We have to do this because can't tell nullptr's apart,..)
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- generalize xo::reflect::TypeDescrBase
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// compose these into Expressions.
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//
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struct type_ref {
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bool is_concrete() const { return td_ && td_->is_concrete(); }
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// generated name, so we can map between types. Don't want to create TypeDescr
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// every time we have a typed location. there'd be a lot of them, and hard to collect
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flatstring<11> id_;
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// if TypeDescr is concrete (fully described), this describes it
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TypeDescr td_;
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};
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// what we know about a type
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//
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struct TypeBlueprint : public Refcounted {
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static bool equal(bp<TypeTemplate> lhs, bp<TypeTemplate> rhs);
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type_ref ref_;
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// additional descriptive info...
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};
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// effectively these are constraints?
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//
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using TypeSubstitutionMap = map<string, rp<TypeTemplate>>;
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will have typeunifier in parserstatemachine
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struct TypeUnifier {
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// extend as unification proceeds
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//
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TypeSubstitutionMap substitutions_;
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};
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alt strategy
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-------------
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