From 165716953fd5ca68a1d9df917147ae948b6fdf2b Mon Sep 17 00:00:00 2001
From: Tristan Morgan <tristanmorgan@users.noreply.github.com>
Date: Tue, 7 May 2024 17:13:34 +1000
Subject: [PATCH] Drop unreachable code.

---
 parser/tokenise.go      |  8 +++++++-
 parser/tokenise_test.go | 27 +++++++++++++++------------
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/parser/tokenise.go b/parser/tokenise.go
index 1160efa..81adb73 100644
--- a/parser/tokenise.go
+++ b/parser/tokenise.go
@@ -51,7 +51,13 @@ func Tokenise(input io.ByteReader) (program []Instruction, err error) {
 			jmpStack = jmpStack[:len(jmpStack)-1]
 			program[pc].operand = jmpPc
 			program[jmpPc].operand = pc
-			if pc-jmpPc == 2 && program[pc-1].SameOp(NewInstruction('+')) {
+			if jmpPc == 1 ||
+				program[jmpPc-1].Complement(Instruction{opSetVal, 0}) ||
+				program[jmpPc-1].SameOp(NewInstruction(']')) {
+				pc = jmpPc
+				program = program[:pc]
+				pc--
+			} else if pc-jmpPc == 2 && program[pc-1].SameOp(NewInstruction('+')) {
 				pc = jmpPc
 				program = program[:pc]
 				program = append(program, Instruction{opSetVal, 0})
diff --git a/parser/tokenise_test.go b/parser/tokenise_test.go
index acde61e..9649dea 100644
--- a/parser/tokenise_test.go
+++ b/parser/tokenise_test.go
@@ -30,9 +30,10 @@ func TestTokenise(t *testing.T) {
 		},
 		{
 			"op_mul",
-			" [<++++++>-]>[->>---<<]",
+			"+[<++++++>-]>[->>---<<]",
 			[]Instruction{
 				{opNoop, 0},
+				{opAddVal, 1},
 				{opMulVal, -1}, // dest value pointer
 				{opNoop, 6},    // multiplication factor
 				{opAddDp, 1},
@@ -58,59 +59,61 @@ func TestTokenise(t *testing.T) {
 		},
 		{
 			"op_skip",
-			"[>>>>>]",
+			">[>>>>>]",
 			[]Instruction{
 				{opNoop, 0},
+				{opAddDp, 1},
 				{opSkip, 5},
 			},
 		},
 		{
 			"op_move",
-			"[->>+<<][<<<+>>>-]",
+			">[->>+<<]>[<<<+>>>-]",
 			[]Instruction{
 				{opNoop, 0},
+				{opAddDp, 1},
 				{opMove, 2},
+				{opAddDp, 1},
 				{opMove, -3},
 			},
 		},
 		{
 			"op_jmp_z_nz",
-			"[->>+>+<<<]",
+			">[->>+>+<<<]",
 			[]Instruction{
 				{opNoop, 0},
-				{opJmpZ, 8},
+				{opAddDp, 1},
+				{opJmpZ, 9},
 				{opAddVal, -1},
 				{opAddDp, 2},
 				{opAddVal, 1},
 				{opAddDp, 1},
 				{opAddVal, 1},
 				{opAddDp, -3},
-				{opJmpNz, 1},
+				{opJmpNz, 2},
 			},
 		},
 		{
 			"op_nested",
-			"[[[[[[[,]]]]]]][comment.]",
+			">[[[[[[[,]]]]]]][comment.]",
 			[]Instruction{
 				{opNoop, 0},
+				{opAddDp, 1},
+				{opJmpZ, 16},
 				{opJmpZ, 15},
 				{opJmpZ, 14},
 				{opJmpZ, 13},
 				{opJmpZ, 12},
 				{opJmpZ, 11},
 				{opJmpZ, 10},
-				{opJmpZ, 9},
 				{opIn, 1},
+				{opJmpNz, 8},
 				{opJmpNz, 7},
 				{opJmpNz, 6},
 				{opJmpNz, 5},
 				{opJmpNz, 4},
 				{opJmpNz, 3},
 				{opJmpNz, 2},
-				{opJmpNz, 1},
-				{opJmpZ, 18},
-				{opOut, 1},
-				{opJmpNz, 16},
 			},
 		},
 	}