Move pretty-printed "Running at..." header to logging.js + re-arrange logging.js exports

logging.js

@@ -1,4 +1,4 @@
-exports.logMemory = (x) => {
+const logMemory = (x) => {
   console.log(`┌────────┬────────┬────────┐`);
   console.log(`│  addr  │   op   │   arg  │`);
   console.log(`├────────┼────────┼────────┤`);
@@ -11,6 +11,20 @@ exports.logMemory = (x) => {
   console.log(`└────────┴────────┴────────┘`);
 }
 
-const num2hex = (num) => num.toString(16).toUpperCase().padStart(2, "0");
+const logRunningHeader = () => {
+  console.log();
+  let time = new Date();
+  console.log( `┌─────────────────────┐`);
+  console.log( `│ Running at ${time.toLocaleTimeString('en-GB')} │` );
+  console.log( `└─────────────────────┘`);
+}
 
-exports.num2hex = num2hex;
+const num2hex = (num) => num.toString(16).toUpperCase().padStart(2, "0");
+const hex2num = (hex) => parseInt(hex, 16);
+
+module.exports = {
+  "logMemory": logMemory,
+  "logRunningHeader": logRunningHeader,
+  "num2hex": num2hex,
+  "hex2num": hex2num,
+}

simulator.js

@@ -1,4 +1,5 @@
 const { INITIAL_IP_ADDRESS, CYCLE_LIMIT } = require('./machine.config');
+const { logRunningHeader, num2hex } = require('./logging.js');
 const display = require('./display.js');
 
 // STATE
@@ -76,7 +77,14 @@ const Instructions = {
 
   sub_lit: (lit) => { // TODO: carry flag
     console.log("SUB lit");
-    CPU.Acc = CPU.Acc - lit;
+    let sum = CPU.Acc - lit;
+    if (sum < 0) {
+      CPU.CF = 1;
+      CPU.Acc = (sum % 15) + 1; // FIXME ???
+    } else {
+      CPU.CF = 0;
+      CPU.Acc = sum;
+    }
     CPU.IP = CPU.IP += 2;
   },
 
@@ -193,17 +201,3 @@ function logCPUState() {
   console.log( `IP: ${CPU.IP}   Acc: ${CPU.Acc}   CF: ${CPU.CF}   ${CPU.running ? "running" : "halted" }` );
   console.log();
 };
-
-
-// FUNCTIONS FOR DISPLAYING DATA
-
-function num2hex(num) { return num.toString(16) };
-function hex2num(hex) { return parseInt(hex, 16) };
-
-function logRunningHeader() {
-  console.log();
-  let time = new Date();
-  console.log( `┌─────────────────────┐`);
-  console.log( `│ Running at ${time.toLocaleTimeString('en-GB')} │` );
-  console.log( `└─────────────────────┘`);
-}