From 7c76bc49af8b6805488ffdffec94829b29c88428 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Mon, 15 Feb 2021 15:35:40 -0500
Subject: [PATCH] remove special-case : ; from parser

---
 builtins.go | 17 +++++++++++++++++
 eval.go     | 24 ++++++------------------
 main.go     | 31 ++++++++++++++++++++++---------
 3 files changed, 45 insertions(+), 27 deletions(-)

diff --git a/builtins.go b/builtins.go
index 560e8b8..30b4cb3 100644
--- a/builtins.go
+++ b/builtins.go
@@ -8,6 +8,23 @@ type Builtins struct{}
 // ErrExit is a special sentinel value to cease computation and quit
 var ErrExit = fmt.Errorf("exit requested")
 
+// Colon sets the COMPILE/IMMEDIATE flag to COMPILE
+func (b *Builtins) Colon(f *bool) func() error {
+	return func() error {
+		*f = false
+		return nil
+	}
+}
+
+// Semicolon sets the COMPILE/IMMEDIATE flag back to IMMEDIATE and adds the defintion to the dictionary
+func (b *Builtins) Semicolon(c *Context) func() error {
+	return func() error {
+		c.Dictionary.AddWord(c.Words[0], nil, c.Words[1:], false)
+		c.Immediate = true
+		return nil
+	}
+}
+
 // Eq compares TOS and NOS and puts -1 on the stack if they're equal, 0 otherwise.
 func (b *Builtins) Eq(s *Stack) func() error {
 	return func() error {
diff --git a/eval.go b/eval.go
index aa70682..ede9315 100644
--- a/eval.go
+++ b/eval.go
@@ -11,15 +11,15 @@ type Context struct {
 	Dictionary Dictionary
 	Stack      *Stack
 	RStack     *Stack
+	Immediate  bool
+	Words      []string
 }
 
 // Eval evaulates a given line, recursively descending into given words as needed
 func (c *Context) Eval(line string) error {
 	// state
 	var word []byte
-	var words []string
 	var comment bool
-	immediate := true
 
 	for i := 0; i < len(line); i = i + 1 {
 		switch line[i] {
@@ -34,28 +34,16 @@ func (c *Context) Eval(line string) error {
 			} else {
 				word = append(word, line[i])
 			}
-		case ':', ';': // COMPILE/IMMEDIATE mode swapping
-			if len(word) == 0 {
-				if line[i] == ':' {
-					immediate = false
-				} else if line[i-1] == ' ' && line[i] == ';' {
-					c.Dictionary.AddWord(words[0], nil, words[1:], false)
-					word = []byte{}
-					immediate = true
-				}
-			} else {
-				word = append(word, line[i])
-			}
 		case ' ':
 			sword := strings.TrimSpace(string(word))
-			if !immediate { // continue building our subroutine if we're not in immediate mode...
+			if !c.Immediate { // continue building our subroutine if we're not in immediate mode...
 				if len(word) != 0 { // don't add empty words to our list
 					// Was that a word we know?
 					w, _ := c.Dictionary.GetWord(sword)
 					// check if it's an IMMEDIATE mode toggle word
-					immediate = w.Immediate
-					if !immediate {
-						words = append(words, sword)
+					c.Immediate = w.Immediate
+					if !c.Immediate {
+						c.Words = append(c.Words, sword)
 						word = []byte{}
 						continue
 					}
diff --git a/main.go b/main.go
index 7ba8868..ed7808a 100644
--- a/main.go
+++ b/main.go
@@ -13,12 +13,29 @@ func main() {
 	rstack := Stack{values: []int{}}
 
 	dict := Dictionary{}
+
+	c := Context{
+		Dictionary: dict,
+		Stack:      &stack,
+		RStack:     &rstack,
+		Immediate:  true,
+		Words:      []string{},
+	}
+
 	b := &Builtins{}
+	// word definitions
+	dict.AddWord(":", b.Colon(&c.Immediate), nil, false)
+	dict.AddWord(";", b.Semicolon(&c), nil, true)
+	// math
 	dict.AddWord("+", b.Add(&stack), nil, false)
 	dict.AddWord("-", b.Sub(&stack), nil, false)
 	dict.AddWord("*", b.Mul(&stack), nil, false)
 	dict.AddWord("/", b.Div(&stack), nil, false)
+	// output
 	dict.AddWord(".", b.Print(&stack), nil, false)
+	dict.AddWord("EMIT", b.Emit(&stack), nil, false)
+	dict.AddWord("CR", b.CR(), nil, false)
+	// logic
 	dict.AddWord("=", b.Eq(&stack), nil, false)
 	dict.AddWord("0=", nil, []string{"0", "="}, false)
 	dict.AddWord("<>", b.NEq(&stack), nil, false)
@@ -28,29 +45,25 @@ func main() {
 	dict.AddWord("<=", b.LtEq(&stack), nil, false)
 	dict.AddWord("0<", nil, []string{"0", "<"}, false)
 	dict.AddWord("0>", nil, []string{"0", ">"}, false)
+	// stack manipulation
 	dict.AddWord("DUP", b.Dup(&stack), nil, false)
 	dict.AddWord("SWAP", b.Swap(&stack), nil, false)
 	dict.AddWord("OVER", b.Over(&stack), nil, false)
 	dict.AddWord("DROP", b.Drop(&stack), nil, false)
 	dict.AddWord("ROT", b.Rot(&stack), nil, false)
+	// debugging
 	dict.AddWord("WORDS", b.Words(dict), nil, false)
 	dict.AddWord(".S", b.Debug(&stack), nil, false)
 	dict.AddWord(".R", b.Debug(&rstack), nil, false)
-	dict.AddWord("EMIT", b.Emit(&stack), nil, false)
 	dict.AddWord("R>", b.RFrom(&stack, &rstack), nil, false)
 	dict.AddWord(">R", b.ToR(&stack, &rstack), nil, false)
 	dict.AddWord("R@", b.RFetch(&stack, &rstack), nil, false)
+	// branching
 	dict.AddWord("DO", b.Do(&stack, &rstack), nil, false)
 	dict.AddWord("LOOP", b.Loop(&stack, &rstack), nil, false)
 	dict.AddWord("I", b.I(&stack, &rstack), nil, false)
-	dict.AddWord("CR", b.CR(), nil, false)
-	dict.AddWord("QUIT", b.Quit(), nil, false)
-
-	c := Context{
-		Dictionary: dict,
-		Stack:      &stack,
-		RStack:     &rstack,
-	}
+	// exit
+	dict.AddWord("BYE", b.Quit(), nil, false)
 
 	reader := bufio.NewReader(os.Stdin)
 	fmt.Print("prosper")