24 lines
1 KiB
Text
24 lines
1 KiB
Text
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Variable f {A : Type} (a : A) : A
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Variable a : Int
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Variable b : Real
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Definition tst : Bool := (fun x y, (f x) > (f y)) a b
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(*
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In the current version, the example above does not work without user's help.
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We can compile this example into the following elaborator problem:
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Definition tst : Bool := (fun (x : _) (y : _),
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((choice Nat::lt Int::lt Real::lt)
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((choice id nat_to_int nat_to_real int_to_real) (f _ x))
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((choice id nat_to_int nat_to_real int_to_real) (f _ y))))
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a b
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The first choice construct is generated because > is overloaded notation.
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The second and third choices are selected because Nat::lt, Int::lt and
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Real::lt expect Nat, Int and Real arguments respectively.
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The type of the expressions (f _ x) and (f _ y) is unknown at problem generation time.
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So, we create a choice with all relevant coercions. The choice `id` represents "no coercion" is
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needed.
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*)
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Definition tst : Bool := (fun x y, (int_to_real (f x)) > (f y)) a b
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