28 lines
1.0 KiB
Plaintext
28 lines
1.0 KiB
Plaintext
;;;; Comparing enums, which type checked and then died in the backend.
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;;;;
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;;;; Types.is_comparable admits an enum, so the checker was stating an intent
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;;;; emit never honoured: (= k :a) passed check and then raised
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;;;; Failure("comparison on K") with no source location. An enum is an i32 at
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;;;; run time, so all six operators lower to icmp.
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(defenum K [lo -1 mid 0 hi 1])
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(defstruct S [k K])
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(defn is-eq [k K] bool (= k :mid))
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(defn is-below [k K] bool (< k :mid))
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(defn main [] i32
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;; Equality, both ways round.
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(println (if (is-eq :mid) "eq yes" "eq no"))
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(println (if (is-eq :hi) "eq yes" "eq no"))
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;; Ordering, and signed: lo is -1, so an unsigned compare would call it the
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;; largest member and answer the other way.
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(println (if (is-below :lo) "lo below mid" "lo not below mid"))
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(println (if (is-below :hi) "hi below mid" "hi not below mid"))
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;; And through a struct field, which is a different path to the same compare.
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(let [s (S {.k :hi})]
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(println (if (= (.k s) :hi) "field eq yes" "field eq no")))
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0)
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