1 files changed, 7 insertions, 2 deletions
diff --git a/double.h b/double.h
index 0c42b04..077b4b8 100644
--- a/double.h
+++ b/double.h
@@ -1,3 +1,6 @@
+#ifndef DOUBLE_H
+#define DOUBLE_H
+
 #include <stdbool.h>
 
 double int_to_valuetype(int);
@@ -24,6 +27,8 @@ double power(double,double);
 
 double to_double(double);
 
-double to_string(char*,double);
+int to_string(char*,double);
+
+int root_to_string(char*,double,double);
 
-double root_to_string(char*,double,double);
+#endif