68 lines
2.0 KiB
D
68 lines
2.0 KiB
D
import std.stdio, std.traits;
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void fourBitsAdder(T)(in T a0, in T a1, in T a2, in T a3,
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in T b0, in T b1, in T b2, in T b3,
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out T o0, out T o1,
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out T o2, out T o3,
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out T overflow) pure nothrow @nogc {
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// A XOR using only NOT, AND and OR, as task requires.
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static T xor(in T x, in T y) pure nothrow @nogc {
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return (~x & y) | (x & ~y);
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}
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static void halfAdder(in T a, in T b,
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out T s, out T c) pure nothrow @nogc {
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s = xor(a, b);
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// s = a ^ b; // The built-in D xor.
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c = a & b;
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}
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static void fullAdder(in T a, in T b, in T ic,
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out T s, out T oc) pure nothrow @nogc {
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T ps, pc, tc;
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halfAdder(/*in*/a, b, /*out*/ps, pc);
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halfAdder(/*in*/ps, ic, /*out*/s, tc);
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oc = tc | pc;
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}
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T zero, tc0, tc1, tc2;
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fullAdder(/*in*/a0, b0, zero, /*out*/o0, tc0);
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fullAdder(/*in*/a1, b1, tc0, /*out*/o1, tc1);
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fullAdder(/*in*/a2, b2, tc1, /*out*/o2, tc2);
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fullAdder(/*in*/a3, b3, tc2, /*out*/o3, overflow);
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}
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void main() {
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alias T = size_t;
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static assert(isUnsigned!T);
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enum T one = T.max,
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zero = T.min,
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a0 = zero, a1 = one, a2 = zero, a3 = zero,
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b0 = zero, b1 = one, b2 = one, b3 = one;
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T s0, s1, s2, s3, overflow;
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fourBitsAdder(/*in*/ a0, a1, a2, a3,
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/*in*/ b0, b1, b2, b3,
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/*out*/s0, s1, s2, s3, overflow);
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writefln(" a3 %032b", a3);
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writefln(" a2 %032b", a2);
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writefln(" a1 %032b", a1);
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writefln(" a0 %032b", a0);
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writefln(" +");
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writefln(" b3 %032b", b3);
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writefln(" b2 %032b", b2);
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writefln(" b1 %032b", b1);
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writefln(" b0 %032b", b0);
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writefln(" =");
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writefln(" s3 %032b", s3);
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writefln(" s2 %032b", s2);
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writefln(" s1 %032b", s1);
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writefln(" s0 %032b", s0);
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writefln("overflow %032b", overflow);
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}
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