Day 21 solution

Hopefully my logic is explained well enough in the comments for this one. We're just layering more programming languages on top of other programming languages. This is how you anger the computer gods and bring about the AI singularity.

I also made some general tweaks to the Intcode machine to make ASCII intcode machines dead simple to deal with. Is it worth the extra branches for each input and output instruction in the interpreter? Probably not...but I was never going to win any speed competitions anyway.

utilities/intcode.go

@@ -28,6 +28,8 @@ type IntcodeProgram struct {
 	program       []int64
 	relativeBase  int
 	haltRequested bool
+	printASCII    bool
+	feedInput     []rune
 }
 
 type IntcodeProgramState struct {
@@ -140,14 +142,15 @@ func (p *IntcodeProgram) Reset() {
 	p.relativeBase = 0
 }
 
-func (p *IntcodeProgram) Run() {
-	p.RunIn(func(int) int64 { return 0 }, func(int64, IntcodeProgramState) {})
+func (p *IntcodeProgram) Run() int64 {
+	return p.RunIn(func(int) int64 { return 0 }, func(int64, IntcodeProgramState) {})
 }
 
-func (p *IntcodeProgram) RunIn(inputFunc ProvideInputFunc, outputFunc ReceiveOutputFunc) {
+func (p *IntcodeProgram) RunIn(inputFunc ProvideInputFunc, outputFunc ReceiveOutputFunc) int64 {
 	p.init()
 
 	inputsRequested := 0
+	lastOutput := int64(0)
 	for instructionPointer := 0; instructionPointer < len(p.program) && !p.haltRequested; {
 		instruction := p.GetMemory(instructionPointer)
 		instructionPointer++
@@ -184,13 +187,28 @@ func (p *IntcodeProgram) RunIn(inputFunc ProvideInputFunc, outputFunc ReceiveOut
 		case opInput:
 			inputsRequested++
 			param1 := p.GetMemory(instructionPointer)
-			p.setMemory(int(param1), inputFunc(inputsRequested), paramModes[0])
+			var inputVal int64
+			if len(p.feedInput) > 0 {
+				inputVal = int64(p.feedInput[0])
+				p.feedInput = p.feedInput[1:]
+			} else {
+				inputVal = inputFunc(inputsRequested)
+			}
+			if p.printASCII && inputVal <= 255 {
+				fmt.Printf("%c", rune(inputVal))
+			}
+			p.setMemory(int(param1), inputVal, paramModes[0])
 
 			instructionPointer += 1
 
 		case opOutput:
 			param1 := p.GetMemory(instructionPointer)
-			outputFunc(p.getParamValue(int(param1), paramModes[0]), p.makeState(instructionPointer))
+			param1Val := p.getParamValue(int(param1), paramModes[0])
+			if p.printASCII && param1Val <= 255 {
+				fmt.Printf("%c", rune(param1Val))
+			}
+			outputFunc(param1Val, p.makeState(instructionPointer))
+			lastOutput = param1Val
 
 			instructionPointer += 1
 
@@ -256,8 +274,19 @@ func (p *IntcodeProgram) RunIn(inputFunc ProvideInputFunc, outputFunc ReceiveOut
 	}
 
 	p.haltRequested = false
+
+	return lastOutput
 }
 
 func (p *IntcodeProgram) Stop() {
 	p.haltRequested = true
 }
+
+func (p *IntcodeProgram) SetDebugASCIIPrint(enable bool) {
+	p.printASCII = enable
+}
+
+func (p *IntcodeProgram) FeedInputString(str string) {
+	p.feedInput = make([]rune, len(str))
+	copy(p.feedInput, []rune(str))
+}