2 files changed, 47 insertions, 0 deletions
diff --git a/parser/parser.go b/parser/parser.go
index 6645da1..a2ea590 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -139,6 +139,8 @@ func (p *Parser) parseIdentifier() ast.Expression {
 
 // parseIntegerLiteral parses an integer literal.
 func (p *Parser) parseIntegerLiteral() ast.Expression {
+	defer untrace(trace("parseIntegerLiteral"))
+
 	var lit *ast.IntegerLiteral = &ast.IntegerLiteral{Token: p.curToken}
 
 	var value, err = strconv.ParseInt(p.curToken.Literal, 0, 64)
@@ -195,6 +197,8 @@ func (p *Parser) parseReturnStatement() *ast.ReturnStatement {
 
 // parseExpressionStatement parses an expression statement.
 func (p *Parser) parseExpressionStatement() *ast.ExpressionStatement {
+	defer untrace(trace("parseExpressionStatement"))
+
 	var stmt *ast.ExpressionStatement = &ast.ExpressionStatement{Token: p.curToken}
 
 	stmt.Expression = p.parseExpression(LOWEST)
@@ -215,6 +219,8 @@ func (p *Parser) noPrefixParseFnError(t tokens.TokenType) {
 
 // parseExpression parses an expression.
 func (p *Parser) parseExpression(precedence int) ast.Expression {
+	defer untrace(trace("parseExpression"))
+
 	prefix := p.prefixParseFns[p.curToken.Type]
 
 	if prefix == nil {
@@ -242,6 +248,8 @@ func (p *Parser) parseExpression(precedence int) ast.Expression {
 
 // parsePrefixExpression parses a prefix expression.
 func (p *Parser) parsePrefixExpression() ast.Expression {
+	defer untrace(trace("parsePrefixExpression"))
+
 	var expression *ast.PrefixExpression = &ast.PrefixExpression{
 		Token:    p.curToken,
 		Operator: p.curToken.Literal,
@@ -256,6 +264,8 @@ func (p *Parser) parsePrefixExpression() ast.Expression {
 
 // parseInfixExpression parses an infix expression.
 func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression {
+	defer untrace(trace("parseInfixExpression"))
+
 	expression := &ast.InfixExpression{
 		Token:    p.curToken,
 		Operator: p.curToken.Literal,
diff --git a/parser/parser_tracing.go b/parser/parser_tracing.go
new file mode 100644
index 0000000..a0819da
--- /dev/null
+++ b/parser/parser_tracing.go
@@ -0,0 +1,37 @@
+package parser
+
+import (
+	"fmt"
+	"strings"
+)
+
+var traceLevel int = 0
+
+const traceIdentPlaceholder string = "\t"
+
+func identLevel() string {
+	return strings.Repeat(traceIdentPlaceholder, traceLevel-1)
+}
+
+func tracePrint(fs string) {
+	fmt.Printf("%s%s\n", identLevel(), fs)
+}
+
+func incIdent() {
+	traceLevel = traceLevel + 1
+}
+
+func decIdent() {
+	traceLevel = traceLevel - 1
+}
+
+func trace(msg string) string {
+	incIdent()
+	tracePrint("BEGIN " + msg)
+	return msg
+}
+
+func untrace(msg string) {
+	tracePrint("END " + msg)
+	decIdent()
+}
+\ No newline at end of file