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structure ROOT =
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struct
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structure IntDef =
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struct
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datatype nat = Zero_nat | Succ_nat of nat;
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fun less_nat Zero_nat (Succ_nat n) = true
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| less_nat n Zero_nat = false
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| less_nat (Succ_nat m) (Succ_nat n) = less_nat m n;
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fun minus_nat (Succ_nat m) (Succ_nat n) = minus_nat m n
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| minus_nat Zero_nat n = Zero_nat
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| minus_nat y Zero_nat = y;
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end; (*struct IntDef*)
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structure Codegen =
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struct
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fun pick ((k, v) :: xs) n =
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(if IntDef.less_nat n k then v else pick xs (IntDef.minus_nat n k))
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| pick (x :: xs) n =
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let
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val (ka, va) = x;
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in
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(if IntDef.less_nat n ka then va else pick xs (IntDef.minus_nat n ka))
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end;
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end; (*struct Codegen*)
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end; (*struct ROOT*)
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