add clear func to repl

repl/commands.go

@@ -0,0 +1,12 @@
+package repl
+
+import (
+	"os"
+	"os/exec"
+)
+
+func clearOutput() {
+	cmd := exec.Command("clear")
+	cmd.Stdout = os.Stdout
+	cmd.Run()
+}

repl/repl.go

@@ -21,6 +21,12 @@ func Start(in io.Reader, out io.Writer) {
 			return
 		}
 		line := scanner.Text()
+
+		if line == "clear" {
+			clearOutput()
+			continue
+		}
+
 		l := lexer.New(line)
 
 		for tok := l.NextToken(); tok.Type != token.EOF; tok = l.NextToken() {