fix: printing for ast giving segmentation violation

README.md

@@ -73,6 +73,11 @@ go build -o ninja-lang
 
 For more detail about language, you can check [here](https://ninja.jonathan.pt) (Still working in progress).  
 
+# Demo  
+
+Resolving katas you can check this repository  
+https://adventofcode.com/2015  
+
 # Syntax  
 
 ## Variable  

ast/for_statement.go

@@ -21,11 +21,26 @@ func (fs *ForStatement) String() string {
 	out.WriteString(string(fs.TokenLiteral()) + " ")
 
 	out.WriteString("(")
-	out.WriteString(fs.InitialCondition.String() + ";")
-	out.WriteString(fs.Condition.String() + ";")
-	out.WriteString(fs.Iteration.String())
+	if fs.InitialCondition != nil {
+		out.WriteString(fs.InitialCondition.String())
+	} else {
+		out.WriteString(";")
+	}
+
+	if fs.Condition != nil {
+		out.WriteString(fs.Condition.String() + ";")
+	} else {
+		out.WriteString(";")
+	}
+
+	if fs.Iteration != nil {
+		out.WriteString(fs.Iteration.String())
+	}
+
 	out.WriteString(") ")
+	out.WriteString("{")
 	out.WriteString(fs.Body.String())
+	out.WriteString("}")
 
 	return out.String()
 }

main.go

@@ -19,6 +19,7 @@ var version string
 
 func main() {
 	exec := flag.StringP("exec", "e", "", "Runs the given code.")
+	_ = flag.BoolP("ast", "a", false, "Return AST structure")
 
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr, "Version: %s. \nUsage: ninja [flags] [program file] [arguments]\n\nAvailable flags:\n", version)
@@ -64,6 +65,8 @@ func execCode(input string, writer io.Writer) {
 		return
 	}
 
+	fmt.Println(program.String())
+
 	evaluated := evaluator.Eval(program, env)
 	if evaluated != nil {
 		fmt.Fprintf(writer, evaluated.Inspect())

parser/for_test.go

@@ -51,3 +51,46 @@ func TestForStatement(t *testing.T) {
 		}
 	}
 }
+
+func TestForStatement_String(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{
+			`for(var i = 0; i <= 3; i = i + 1) { }`,
+			`for (var i = 0;(i <= 3);i = (i + 1);) {}`,
+		},
+		{
+			`for(var i = 0; i <= 3; i = i + 1) { puts(1); }`,
+			`for (var i = 0;(i <= 3);i = (i + 1);) {puts(1)}`,
+		},
+		{
+			`for(; i <= 3; i = i + 1) { puts(1); }`,
+			`for (;(i <= 3);i = (i + 1);) {puts(1)}`,
+		},
+		{
+			`for(var i = 0;; i = i + 1) { puts(1); }`,
+			`for (var i = 0;;i = (i + 1);) {puts(1)}`,
+		},
+		{
+			`for(var i = 0; i <= 3;) { puts(1); }`,
+			`for (var i = 0;(i <= 3);) {puts(1)}`,
+		},
+		{
+			`for(;;) { puts(1); }`,
+			`for (;;) {puts(1)}`,
+		},
+	}
+
+	for _, tt := range tests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		if program.String() != tt.expected {
+			t.Errorf("ForStatement.string() expected %s. Got: %s", tt.expected, program.String())
+		}
+	}
+}