mirror of
https://github.com/kanaka/mal.git
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79 lines
2.3 KiB
Plaintext
79 lines
2.3 KiB
Plaintext
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;;
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;; equality.mal
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;;
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;; This file checks whether the `=` function correctly implements equality of
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;; hash-maps and sequences (lists and vectors). If not, it redefines the `=`
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;; function with a pure mal (recursive) implementation that only relies on the
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;; native original `=` function for comparing scalars (integers, booleans,
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;; symbols, strings).
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;;
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;; Save the original (native) `=` as scalar-equal?
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(def! scalar-equal? =)
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;; A simple `and` macro for two argument which doesn't use `=` internally
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(defmacro! and2
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(fn* [a b]
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`(let* (and2_FIXME ~a)
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(if and2_FIXME ~b and2_FIXME))))
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;; Implement `=` for two sequential arguments
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(def! sequential-equal?
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(fn* [a b]
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(if (scalar-equal? (count a) (count b))
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(if (empty? a)
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true
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(if (mal-equal? (first a) (first b))
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(sequential-equal? (rest a) (rest b))
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false))
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false)))
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;; Helper function
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(def! hash-map-vals-equal?
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(fn* [a b map-keys]
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(if (scalar-equal? 0 (count map-keys))
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true
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(let* [key (first map-keys)]
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(if (and2
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(and2 (contains? a key) (contains? b key))
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(mal-equal? (get a key) (get b key)))
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(hash-map-vals-equal? a b (rest map-keys))
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false)))))
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;; Implement `=` for two hash-maps
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(def! hash-map-equal?
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(fn* [a b]
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(let* [keys-a (keys a)]
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(if (scalar-equal? (count keys-a) (count (keys b)))
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(hash-map-vals-equal? a b keys-a)
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false))))
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;; This implements = in pure mal (using only scalar-equal? as native impl)
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(def! mal-equal?
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(fn* [a b]
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(cond
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(and2 (sequential? a) (sequential? b)) (sequential-equal? a b)
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(and2 (map? a) (map? b)) (hash-map-equal? a b)
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true (scalar-equal? a b))))
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(def! hash-map-equality-correct?
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(fn* []
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(try*
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(and2 (= {:a 1} {:a 1})
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(not (= {:a 1} {:a 1 :b 2})))
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(catch* _ false))))
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(def! sequence-equality-correct?
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(fn* []
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(try*
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(and2 (= [:a :b] (list :a :b))
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(not (= [:a :b] [:a :b :c])))
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(catch* _ false))))
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;; If the native `=` implementation doesn't support sequences or hash-maps
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;; correctly, replace it with the pure mal implementation
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(if (not (and2 (hash-map-equality-correct?) (sequence-equality-correct?)))
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(do
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(def! = mal-equal?)
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(println "equality.mal: Replaced = with pure mal implementation")))
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