self param replaced as opTerm

operator-fact.go

@@ -18,10 +18,10 @@ func newFactTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalFact(ctx ExprContext, self *term) (v any, err error) {
+func evalFact(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue any
 
-	if leftValue, err = self.evalPrefix(ctx); err != nil {
+	if leftValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
@@ -36,7 +36,7 @@ func evalFact(ctx ExprContext, self *term) (v any, err error) {
 			err = fmt.Errorf("factorial of a negative integer (%d) is not allowed", i)
 		}
 	} else {
-		err = self.errIncompatibleType(leftValue)
+		err = opTerm.errIncompatibleType(leftValue)
 	}
 	return
 }