35 lines
1002 B
Clojure
35 lines
1002 B
Clojure
(ns rosettacode.adder
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(:use clojure.test))
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(defn xor-gate [a b]
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(or (and a (not b)) (and b (not a))))
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(defn half-adder [a b]
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"output: (S C)"
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(cons (xor-gate a b) (list (and a b))))
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(defn full-adder [a b c]
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"output: (C S)"
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(let [HA-ca (half-adder c a)
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HA-ca->sb (half-adder (first HA-ca) b)]
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(cons (or (second HA-ca) (second HA-ca->sb))
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(list (first HA-ca->sb)))))
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(defn n-bit-adder
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"first bits on the list are low order bits
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1 = true
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2 = false true
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3 = true true
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4 = false false true..."
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can add numbers of different bit-length
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([a-bits b-bits] (n-bit-adder a-bits b-bits false))
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([a-bits b-bits carry]
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(let [added (full-adder (first a-bits) (first b-bits) carry)]
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(if(and (nil? a-bits) (nil? b-bits))
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(if carry (list carry) '())
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(cons (second added) (n-bit-adder (next a-bits) (next b-bits) (first added)))))))
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;use:
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(n-bit-adder [true true true true true true] [true true true true true true])
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=> (false true true true true true true)
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