2016 Update

Task/Four-bit-adder/Lua/four-bit-adder.lua

@@ -1,64 +1,52 @@
 -- Build XOR from AND, OR and NOT
-function xor (a, b)
-	return (a and not b) or (b and not a)
-end
+function xor (a, b) return (a and not b) or (b and not a) end
 
 -- Can make half adder now XOR exists
-function halfAdder (a, b)
-	local sum, carry
-	sum = xor(a, b)
-	carry = a and b
-	return sum, carry
-end
+function halfAdder (a, b) return xor(a, b), a and b end
 
 -- Full adder is two half adders with carry outputs OR'd
 function fullAdder (a, b, cIn)
-	local ha0s, ha0c = halfAdder(cIn, a)
-	local ha1s, ha1c = halfAdder(ha0s, b)
-	local cOut, s = ha0c or ha1c, ha1s
-	return cOut, s
+    local ha0s, ha0c = halfAdder(cIn, a)
+    local ha1s, ha1c = halfAdder(ha0s, b)
+    local cOut, s = ha0c or ha1c, ha1s
+    return cOut, s
 end
 
 -- Carry bits 'ripple' through adders, first returned value is overflow
 function fourBitAdder (a3, a2, a1, a0, b3, b2, b1, b0) -- LSB-first
-	local fa0c, fa0s = fullAdder(a0, b0, false)
-	local fa1c, fa1s = fullAdder(a1, b1, fa0c)
-	local fa2c, fa2s = fullAdder(a2, b2, fa1c)
-	local fa3c, fa3s = fullAdder(a3, b3, fa2c)
-	return fa3c, fa3s, fa2s, fa1s, fa0s -- Return as MSB-first
+    local fa0c, fa0s = fullAdder(a0, b0, false)
+    local fa1c, fa1s = fullAdder(a1, b1, fa0c)
+    local fa2c, fa2s = fullAdder(a2, b2, fa1c)
+    local fa3c, fa3s = fullAdder(a3, b3, fa2c)
+    return fa3c, fa3s, fa2s, fa1s, fa0s -- Return as MSB-first
 end
 
 -- Take string of noughts and ones, convert to native boolean type
 function toBool (bitString)
-	local boolList, bit = {}
-	for digit = 1, 4 do
-		bit = string.sub(string.format("%04d", bitString), digit, digit)
-		if bit == "0" then table.insert(boolList, false) end
-		if bit == "1" then table.insert(boolList, true) end
-	end
-	return boolList
+    local boolList, bit = {}
+    for digit = 1, 4 do
+        bit = string.sub(string.format("%04d", bitString), digit, digit)
+        if bit == "0" then table.insert(boolList, false) end
+        if bit == "1" then table.insert(boolList, true) end
+    end
+    return boolList
 end
 
 -- Take list of booleans, convert to string of binary digits (variadic)
 function toBits (...)
-	local bitString = ""
-	for i, bool in pairs{...} do
-		if bool then
-			bitString = bitString .. "1"
-		else
-			bitString = bitString .. "0"
-		end
-	end
-	return bitString
+    local bStr = ""
+    for i, bool in pairs{...} do
+        if bool then bStr = bStr .. "1" else bStr = bStr .. "0" end
+    end
+    return bStr
 end
 
 -- Little driver function to neaten use of the adder
 function add (n1, n2)
-	local A, B = toBool(n1), toBool(n2)
-	local v, s0, s1, s2, s3 = fourBitAdder	(	A[1], A[2], A[3], A[4],
-							B[1], B[2], B[3], B[4]
-						)
-	return toBits(s0, s1, s2, s3), v
+    local A, B = toBool(n1), toBool(n2)
+    local v, s0, s1, s2, s3 = fourBitAdder( A[1], A[2], A[3], A[4],
+                                            B[1], B[2], B[3], B[4] )
+    return toBits(s0, s1, s2, s3), v
 end
 
 -- Main procedure (usage examples)