Fix printf the extra interface

eval/evaluator_test.go

@@ -2,11 +2,12 @@ package eval
 
 import (
 	"fmt"
+	"math"
+	"testing"
+
 	"github.com/chermehdi/comet/parser"
 	"github.com/chermehdi/comet/std"
 	"github.com/stretchr/testify/assert"
-	"math"
-	"testing"
 )
 
 func TestEvaluator_Eval_Integers(t *testing.T) {
@@ -561,3 +562,41 @@ func assertFoundInScope(t *testing.T, ev *Evaluator, name string, expectedType s
 func parseOrDie(s string) parser.Node {
 	return parser.New(s).Parse()
 }
+
+func ExampleBuiltinPrintf() {
+	// (anouard24): I'm not pround of this
+	// but i'm still learning Golang
+	// its enough for now
+	tests := []string{
+		`printf("Hi")`,
+		`println()
+		printf("Hi %d", 2021)`,
+		`println()
+		printf("% 7d", 5)`,
+		`println()
+		printf("%s", "Test")`,
+		`println()
+		printf("%8s", "Test")`,
+		`println()
+		printf("%t", true)`,
+		`println()
+		printf("%t", false)`,
+		`println()
+		printf("%04d%9s%t", 7, "Comet ", true)`,
+	}
+	evaluator := NewEvaluator()
+	for _, test := range tests {
+		rootNode := parseOrDie(test)
+		evaluator.Eval(rootNode)
+	}
+
+	// Output:
+	// Hi
+	// Hi 2021
+	//       5
+	// Test
+	//     Test
+	// true
+	// false
+	// 0007   Comet true
+}

std/builtins.go

@@ -35,7 +35,12 @@ var Builtins = []*Builtin{
 				transArgs = append(transArgs, extractPrimitive(args[i]))
 			}
 			format := args[0].(*CometStr)
-			fmt.Printf(format.Value, transArgs)
+
+			if len(transArgs) > 0 {
+				fmt.Printf(format.Value, transArgs...)
+			} else {
+				fmt.Printf(format.Value)
+			}
 			return NopInstance
 		},
 	},