Data commit

Task/Four-bit-adder/Julia/four-bit-adder-1.julia

@@ -0,0 +1,30 @@
+using Printf
+
+xor{T<:Bool}(a::T, b::T) = (a&~b)|(~a&b)
+
+halfadder{T<:Bool}(a::T, b::T) = (xor(a,b), a&b)
+
+function fulladder{T<:Bool}(a::T, b::T, c::T=false)
+    (s, ca) = halfadder(c, a)
+    (s, cb) = halfadder(s, b)
+    (s, ca|cb)
+end
+
+function adder(a::BitArray{1}, b::BitArray{1}, c0::Bool=false)
+    len = length(a)
+    length(b) == len || error("Addend width mismatch.")
+    c = c0
+    s = falses(len)
+    for i in 1:len
+        (s[i], c) = fulladder(a[i], b[i], c)
+    end
+    (s, c)
+end
+
+function adder{T<:Integer}(m::T, n::T, wid::T=4, c0::Bool=false)
+    a = bitpack(digits(m, 2, wid))[1:wid]
+    b = bitpack(digits(n, 2, wid))[1:wid]
+    adder(a, b, c0)
+end
+
+Base.bits(n::BitArray{1}) = join(reverse(int(n)), "")

Task/Four-bit-adder/Julia/four-bit-adder-2.julia

@@ -0,0 +1,18 @@
+xavail = trues(15,15)
+xcnt = 0
+xgoal = 10
+println("Testing adder with 4-bit words:")
+while xcnt < xgoal
+    m = rand(1:15)
+    n = rand(1:15)
+    xavail[m,n] || continue
+    xavail[m,n] = xavail[n,m] = false
+    xcnt += 1
+    (s, c) = adder(m, n)
+    oflow = c ? "*" : ""
+    print(@sprintf "    %2d + %2d = %2d => " m n m+n)
+    println(@sprintf("%s + %s = %s%s",
+                     bits(m)[end-3:end],
+                     bits(n)[end-3:end],
+                     bits(s), oflow))
+end