From a1e10543a4f23356898b0dec65650f8e50d9d2c5 Mon Sep 17 00:00:00 2001
From: Tristan Morgan <tristanmorgan@users.noreply.github.com>
Date: Mon, 25 Mar 2024 15:11:13 +1100
Subject: [PATCH] Tweak tokenise.

---
 README.md          | 30 ++++++++++++++++++++++++------
 parser/tokenise.go | 17 +++++++++--------
 2 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/README.md b/README.md
index 950f56b..96d46f6 100644
--- a/README.md
+++ b/README.md
@@ -6,16 +6,34 @@ BFG is an optimised [Brainfuck](https://esolangs.org/wiki/Brainfuck) interpreter
 
 Uses signed ints for data (platform specific 32/64), memory wraps around at 65535, EOF returns -1.
 
+Buffered output flushes on newline, 200 chars or input.
+
 ## Optimisations
 
-[-] is replaced with a blind set 0 command
+Operates with a instruction parse then execute pattern.
+
+ * loop start/end are calculated up front.
+ * [-] is replaced with a blind set 0 command
+ * repeat ++++ or --- are replaced with a single addition/subtraction
+ * addition/subtraction after zero does a blind set.
+ * repeat >>> or <<< are replaced with a single pointer jump
+ * [>>>] and [<<<] are merged into a skip instruction.
+ * [>>+<<-] and [->>+<<] merged into a move instruction.
+
+for performance comparison see no_optimisation branch.
 
-repeat ++++ or --- are replaced with a single addition/subtraction
+## Usage
 
-addition/subtraction after zero does a blind set.
+    Usage:
+      bf [option] source.bf [input]
+    
+    Options:
+      -version
+    	    display version
 
-repeat >>> or <<< are replaced with a single pointer jump
+May use - as source to read program from STDIN and output is STDOUT
 
-[>>+<<-] and [->>+<<] merged into a move instruction.
+    +++++++++[>++++++++>++++++++++++>++++>++++++++++++>+++++++++++>+<<<<<<-]>---.>++
+    .----.+++++.++++++++++.>----.<-----.>>----.+.<<-.>.<<---.>-.>>>--.<.+++++.<<<+++
+    +.>+++.>>>++.<---.<+.>>>+.
 
-buffered output prints on newline, 200 chars or input.
diff --git a/parser/tokenise.go b/parser/tokenise.go
index c896f28..f7a233a 100644
--- a/parser/tokenise.go
+++ b/parser/tokenise.go
@@ -18,28 +18,29 @@ func Tokenise(input io.ByteReader) (program []Instruction, err error) {
 		} else if err != nil {
 			return nil, errors.New("tokenisation read error")
 		}
-		program = append(program, NewInstruction(chr))
-		switch program[pc].operator {
+		instruction := NewInstruction(chr)
+		program = append(program, instruction)
+		switch instruction.operator {
 		case opNoop:
 			program = program[:pc]
 			pc--
 		case opAddDp:
-			if program[pc-1].SameOp(program[pc]) {
-				program[pc-1].operand += program[pc].operand
+			if program[pc-1].SameOp(instruction) {
+				program[pc-1].operand += instruction.operand
 				program = program[:pc]
 				pc--
 			}
 		case opAddVal:
-			if program[pc-1].SameOp(program[pc]) {
-				program[pc-1].operand += program[pc].operand
+			if program[pc-1].SameOp(instruction) {
+				program[pc-1].operand += instruction.operand
 				program = program[:pc]
 				pc--
 			} else if program[pc-1].operator == opSetVal {
-				program[pc-1].operand += program[pc].operand
+				program[pc-1].operand += instruction.operand
 				program = program[:pc]
 				pc--
 			} else if program[pc-1].operator == opJmpNz {
-				operand := program[pc].operand
+				operand := instruction.operand
 				program = program[:pc]
 				program = append(program, Instruction{opSetVal, operand})
 			}