Pretty printer.

README.md

@@ -38,6 +38,8 @@ for performance comparison see no_optimisation branch.
     	    dump parsed program
       -eight
     	    eight bit execution
+      -print
+    	    pretty print parsed program
       -version
     	    display version
 

cmd/bfg/main.go

@@ -25,6 +25,7 @@ func main() {
 	version := flag.Bool("version", false, "display version")
 	eight := flag.Bool("eight", false, "eight bit execution")
 	dump := flag.Bool("dump", false, "dump parsed program")
+	print := flag.Bool("print", false, "pretty print parsed program")
 
 	flag.Usage = func() {
 		fmt.Printf("Usage:\n  %s [option] source.bf [input]\n", os.Args[0])
@@ -35,6 +36,7 @@ func main() {
 	flag.Parse()
 	if *version {
 		fmt.Printf("Version: v%s%s\n", Version, VersionPrerelease)
+		fmt.Println("https://github.com/tristanmorgan/bfg\n")
 		os.Exit(0)
 	}
 
@@ -61,6 +63,8 @@ func main() {
 	}
 	if *dump {
 		parser.Dump(program, outputBuf)
+	} else if *print {
+		parser.Print(program, outputBuf)
 	} else if *eight {
 		data := make([]byte, parser.DataSize)
 		parser.Execute(data, program, inputBuf, outputBuf)

parser/print.go

@@ -0,0 +1,83 @@
+package parser
+
+import (
+	"bufio"
+	"fmt"
+	"strings"
+)
+
+func abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func repeatDirection(neg, pos string, vect int) string {
+	if vect > 0 {
+		return strings.Repeat(pos, vect)
+	}
+	return strings.Repeat(neg, abs(vect))
+}
+
+func instPrint(inst, lastInst Instruction) string {
+	switch inst.operator {
+	case opAddDp:
+		return repeatDirection("<", ">", inst.operand)
+	case opAddVal:
+		return repeatDirection("-", "+", inst.operand)
+	case opSetVal:
+		prefix := "[-]"
+		if lastInst.IsZeroOp() && inst.operand != 0 {
+			prefix = ""
+		}
+		return prefix + repeatDirection("-", "+", inst.operand)
+	case opOut:
+		return "."
+	case opIn:
+		return ","
+	case opJmpZ:
+		return "["
+	case opJmpNz:
+		return "]"
+	case opMove:
+		return "[-" + repeatDirection("<", ">", inst.operand) + "+" + repeatDirection(">", "<", inst.operand) + "]"
+	case opSkip:
+		return "[" + repeatDirection("<", ">", inst.operand) + "]"
+	case opMulVal:
+		return ""
+	case opNoop:
+		if lastInst.operator == opMulVal {
+			multiplier := strings.Repeat("+", abs(inst.operand))
+			if inst.operand < 0 {
+				multiplier = strings.Repeat("-", abs(inst.operand))
+			}
+			if lastInst.operand > 0 {
+				return "[-" + strings.Repeat(">", lastInst.operand) + multiplier + strings.Repeat("<", lastInst.operand) + "]"
+			}
+			return "[-" + strings.Repeat("<", abs(lastInst.operand)) + multiplier + strings.Repeat(">", abs(lastInst.operand)) + "]"
+		}
+		return ""
+	default:
+		return ""
+	}
+}
+
+// Print pretty prints out the parsed program.
+func Print(program []Instruction, writer *bufio.Writer) {
+	depth := 0
+	startLoop := NewInstruction('[')
+	endLoop := NewInstruction(']')
+	lastInst := NewInstruction('!')
+	for _, inst := range program {
+		if inst.SameOp(endLoop) {
+			depth--
+		}
+		fmt.Fprintln(writer, strings.Repeat("\t", depth), instPrint(inst, lastInst))
+		if inst.SameOp(startLoop) {
+			depth++
+		}
+		lastInst = inst
+	}
+	writer.Flush()
+}

parser/print_test.go

@@ -0,0 +1,31 @@
+package parser
+
+import (
+	"bufio"
+	"bytes"
+	"reflect"
+	"testing"
+)
+
+func TestPrint(t *testing.T) {
+	program := []Instruction{
+		{opNoop, 0},
+		{opAddDp, 5},
+		{opSetVal, 0},
+		{opAddVal, 5},
+		{opMove, 2},
+		{opJmpZ, 7},
+		{opIn, 1},
+		{opJmpNz, 5},
+		{opAddDp, 2},
+	}
+	var buf bytes.Buffer
+	outputBuf := bufio.NewWriter(&buf)
+	Print(program, outputBuf)
+	got := buf.String()
+	want := " \n >>>>>\n [-]\n +++++\n [->>+<<]\n [\n\t ,\n ]\n >>\n"
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got %v want %v", got, want)
+	}
+}

parser/tokenise.go

@@ -57,6 +57,9 @@ func Tokenise(input io.ByteReader) (program []Instruction, err error) {
 				pc--
 			} else if pc-jmpPc == 2 && program[pc-1].SameOp(NewInstruction('+')) {
 				pc = jmpPc
+				if program[jmpPc-1].SameOp(NewInstruction('+')) {
+					pc--
+				}
 				program = program[:pc]
 				program = append(program, Instruction{opSetVal, 0})
 			} else if pc-jmpPc == 2 && program[pc-1].SameOp(NewInstruction('>')) {

parser/tokenise_test.go

@@ -16,7 +16,7 @@ func TestTokenise(t *testing.T) {
 	}{
 		{
 			"small_prog",
-			">>>>>[-]zero+++++>+++++[->>+<<]move>>[>>+<<-]move",
+			">>>>>++[-]zero+++++>+++++[->>+<<]move>>[>>+<<-]move",
 			[]Instruction{
 				{opNoop, 0},
 				{opAddDp, 5},

sample/rot13.bf

@@ -1,5 +1,5 @@
 #!/usr/bin/env bf
 
 ,+[-[>>++++[>++++++++<-]<+<-[>+>+>-[>>>]<[[>+<-]>>+>]<<<<<-]]>>>[-]+>--
-[-[<->+++[-]]]<[++++++++++++<[>-[>+>>]>[+[<+>-]>+>>]<<<<<-]>>[<+>-]>[-[
+[-[<->[-]]]<[++++++++++++<[>-[>+>>]>[+[<+>-]>+>>]<<<<<-]>>[<+>-]>[-[
 -<<[-]>>]<<[<<->>-]>>]<<[<<+>>-]]<[-]<.[-]<,+]