From 7345dcb617db629ccf5a89540a301ecb5e8a0a1f Mon Sep 17 00:00:00 2001
From: Tristan Morgan <tristanmorgan@users.noreply.github.com>
Date: Mon, 14 Oct 2024 10:04:27 +1100
Subject: [PATCH] Implement an iterator for byte to Instruction convertion.

---
 go.mod                     |  2 +-
 parser/instruction.go      | 21 +++++++++++++++++++++
 parser/instruction_test.go |  7 +++++--
 parser/tokenise.go         |  9 +--------
 4 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/go.mod b/go.mod
index c031d70..0134041 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/tristanmorgan/bfg
 
-go 1.22.0
+go 1.23.0
diff --git a/parser/instruction.go b/parser/instruction.go
index c1ec544..31d5ce2 100644
--- a/parser/instruction.go
+++ b/parser/instruction.go
@@ -1,5 +1,10 @@
 package parser
 
+import (
+	"io"
+	"iter"
+)
+
 // Instruction structure for intermediate program
 type Instruction struct {
 	operator Opcode
@@ -37,6 +42,22 @@ var instMap = map[byte]Instruction{
 	']': {opJmpNz, 0},
 }
 
+// Instructions returns an iterator of the instructions.
+func Instructions(input io.ByteReader) iter.Seq[Instruction] {
+	return func(yield func(Instruction) bool) {
+
+		for {
+			chr, err := input.ReadByte()
+			if err == io.EOF {
+				break
+			}
+			if !yield(NewInstruction(chr)) {
+				return
+			}
+		}
+	}
+}
+
 // NewInstruction created from a sourcecode byte
 func NewInstruction(chr byte) Instruction {
 	return instMap[chr]
diff --git a/parser/instruction_test.go b/parser/instruction_test.go
index 00ed84d..7f18bde 100644
--- a/parser/instruction_test.go
+++ b/parser/instruction_test.go
@@ -1,8 +1,10 @@
 package parser
 
 import (
+	"bufio"
 	"fmt"
 	"reflect"
+	"strings"
 	"testing"
 	"unsafe"
 )
@@ -57,15 +59,16 @@ func TestNewInstruction(t *testing.T) {
 		{opJmpNz, 0},
 	}
 
-	for idx, val := range []byte(sourceCode) {
+	idx := 0
+	for got := range Instructions(bufio.NewReader(strings.NewReader(sourceCode))) {
 		t.Run(program[idx].String(), func(t *testing.T) {
-			got := NewInstruction(val)
 			want := program[idx]
 
 			if !reflect.DeepEqual(got, want) {
 				t.Errorf("got %v want %v", got, want)
 			}
 		})
+		idx++
 	}
 }
 
diff --git a/parser/tokenise.go b/parser/tokenise.go
index 36118f3..25201d5 100644
--- a/parser/tokenise.go
+++ b/parser/tokenise.go
@@ -11,14 +11,7 @@ func Tokenise(input io.ByteReader) (program []Instruction, err error) {
 	jmpStack := make([]int, 0)
 	program = append(program, Instruction{opNoop, 0})
 	pc++
-	for {
-		chr, err := input.ReadByte()
-		if err == io.EOF {
-			break
-		} else if err != nil {
-			return nil, errors.New("tokenisation read error")
-		}
-		instruction := NewInstruction(chr)
+	for instruction := range Instructions(input) {
 		program = append(program, instruction)
 		switch instruction.operator {
 		case opNoop: