From e22a844dd47be07acec8e1662e9abe7347d9d4fc Mon Sep 17 00:00:00 2001
From: Sky Johnson <skylearj@gmail.com>
Date: Mon, 9 Jun 2025 09:58:47 -0500
Subject: [PATCH] true/false/nil

---
 parser/ast.go    | 19 +++++++++++++++++++
 parser/parser.go | 11 +++++++++++
 parser/token.go  |  8 +++++++-
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/parser/ast.go b/parser/ast.go
index f1aa459..b90017a 100644
--- a/parser/ast.go
+++ b/parser/ast.go
@@ -67,6 +67,25 @@ type StringLiteral struct {
 func (sl *StringLiteral) expressionNode() {}
 func (sl *StringLiteral) String() string  { return fmt.Sprintf(`"%s"`, sl.Value) }
 
+// BooleanLiteral represents boolean literals
+type BooleanLiteral struct {
+	Value bool
+}
+
+func (bl *BooleanLiteral) expressionNode() {}
+func (bl *BooleanLiteral) String() string {
+	if bl.Value {
+		return "true"
+	}
+	return "false"
+}
+
+// NilLiteral represents nil literal
+type NilLiteral struct{}
+
+func (nl *NilLiteral) expressionNode() {}
+func (nl *NilLiteral) String() string  { return "nil" }
+
 // InfixExpression represents binary operations
 type InfixExpression struct {
 	Left     Expression
diff --git a/parser/parser.go b/parser/parser.go
index 749172e..c8dd8da 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -29,6 +29,9 @@ func NewParser(lexer *Lexer) *Parser {
 	p.registerPrefix(IDENT, p.parseIdentifier)
 	p.registerPrefix(NUMBER, p.parseNumberLiteral)
 	p.registerPrefix(STRING, p.parseStringLiteral)
+	p.registerPrefix(TRUE, p.parseBooleanLiteral)
+	p.registerPrefix(FALSE, p.parseBooleanLiteral)
+	p.registerPrefix(NIL, p.parseNilLiteral)
 	p.registerPrefix(LPAREN, p.parseGroupedExpression)
 
 	p.infixParseFns = make(map[TokenType]func(Expression) Expression)
@@ -153,6 +156,14 @@ func (p *Parser) parseStringLiteral() Expression {
 	return &StringLiteral{Value: p.curToken.Literal}
 }
 
+func (p *Parser) parseBooleanLiteral() Expression {
+	return &BooleanLiteral{Value: p.curTokenIs(TRUE)}
+}
+
+func (p *Parser) parseNilLiteral() Expression {
+	return &NilLiteral{}
+}
+
 func (p *Parser) parseGroupedExpression() Expression {
 	p.nextToken()
 
diff --git a/parser/token.go b/parser/token.go
index dca0bd1..a2e7168 100644
--- a/parser/token.go
+++ b/parser/token.go
@@ -8,6 +8,9 @@ const (
 	IDENT TokenType = iota
 	NUMBER
 	STRING
+	TRUE
+	FALSE
+	NIL
 
 	// Operators
 	ASSIGN // =
@@ -59,7 +62,10 @@ var precedences = map[TokenType]Precedence{
 // lookupIdent checks if an identifier is a keyword
 func lookupIdent(ident string) TokenType {
 	keywords := map[string]TokenType{
-		"var": VAR,
+		"var":   VAR,
+		"true":  TRUE,
+		"false": FALSE,
+		"nil":   NIL,
 	}
 
 	if tok, ok := keywords[ident]; ok {