diff --git a/src/error.hpp b/src/error.hpp
index c045ddc..8beae48 100644
--- a/src/error.hpp
+++ b/src/error.hpp
@@ -3,13 +3,11 @@
 #include <string>
 #include <variant>
 
-using namespace std;
-
 class Error {
 
 public:
-  string message;
-  Error(string _message) : message(_message){};
+  std::string message;
+  Error(std::string _message) : message(_message){};
 };
 
 class Void {};
@@ -26,6 +24,6 @@ template <typename R> bool is_ok(Result<R> r) {
 template <typename R> R Ok(Result<R> r) { return std::get<R>(r); }
 /// enables rewrapping errors in a new Result type
 template <typename R> Error Err(Result<R> r) { return std::get<Error>(r); }
-template <typename R> string err_msg(Result<R> r) {
+template <typename R> std::string err_msg(Result<R> r) {
   return std::get<Error>(r).message;
 }
diff --git a/src/parser.hpp b/src/parser.hpp
index eaea00a..d8835ed 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -8,51 +8,49 @@
 
 enum class ExprType { Binary, Grouping, Unary, Literal, None };
 
-using namespace std;
-
 /// Base class for expressions
 class Expression {
 public:
-  virtual string as_string() = 0; // get string rep for debugging
+  virtual std::string as_string() = 0; // get string rep for debugging
   virtual ~Expression();
 };
 
 /// An expression with two operands
 class Binary : public Expression {
-  unique_ptr<Expression> left;
-  unique_ptr<Token> op;
-  unique_ptr<Expression> right;
+  std::unique_ptr<Expression> left;
+  std::unique_ptr<Token> op;
+  std::unique_ptr<Expression> right;
 
 public:
-  string as_string() override;
+  std::string as_string() override;
   Binary(Expression *_left, Token *_operator, Expression *_right);
   ~Binary();
 };
 
 /// An expression between parentheses
 class Grouping : public Expression {
-  unique_ptr<Expression> expr;
+  std::unique_ptr<Expression> expr;
 
 public:
-  string as_string() override;
+  std::string as_string() override;
   Grouping(Expression *_expr);
   ~Grouping();
 };
 
 /// An expression with one operand (operator is `-`  or `!`)
 class Unary : public Expression {
-  unique_ptr<Token> op;
-  unique_ptr<Expression> right;
+  std::unique_ptr<Token> op;
+  std::unique_ptr<Expression> right;
 
 public:
-  string as_string() override;
+  std::string as_string() override;
   Unary(Token *_operator, Expression *_right);
   ~Unary();
 };
 
 /// empty class that is the type of the Nil value
 class NilType {};
-typedef std::variant<double_t, bool, string, NilType> Value;
+typedef std::variant<double_t, bool, std::string, NilType> Value;
 
 /// encapsulates a value: numeric, string etc
 class Literal : public Expression {
@@ -63,15 +61,15 @@ public:
 
   Literal(NilType v) : value(v){};
   Literal(double_t _numeric) : value(_numeric){};
-  Literal(string _str) : value(_str){};
+  Literal(std::string _str) : value(_str){};
   Literal(bool _boolean) : value(_boolean){};
 
-  string as_string() override;
+  std::string as_string() override;
 };
 
 class Parser {
-  vector<Expression> expressions;
-  vector<Token> tokens;
+  std::vector<Expression> expressions;
+  std::vector<Token> tokens;
   int current_token;
 
   /// returns the current token without moving the pointer;
@@ -92,9 +90,9 @@ class Parser {
   /// checks if the current token is of the specified type and
   /// moves the token forward if so, otherwise throws an exception with
   /// the specified message
-  Result<Token *> consume(Token::Type typ, string message);
+  Result<Token *> consume(Token::Type typ, std::string message);
   /// throws an exception for the specified token with the specified message
-  Error error(Token token, string message);
+  Error error(Token token, std::string message);
   /// tries to parse the token as a primary value (string, number etc)
   Result<Expression *> primary();
   /// tries to parse the tokens as a unary expression
@@ -113,5 +111,5 @@ class Parser {
 
 public:
   /// public method for parsing expressions
-  Result<Expression *> parse(vector<Token> tokenlist);
+  Result<Expression *> parse(std::vector<Token> tokenlist);
 };
diff --git a/src/scanner.hpp b/src/scanner.hpp
index 296548b..c9fb590 100644
--- a/src/scanner.hpp
+++ b/src/scanner.hpp
@@ -6,11 +6,9 @@
 #include <string>
 #include <vector>
 
-using namespace std;
-
 typedef struct {
   bool had_error;
-  vector<Token> token_list;
+  std::vector<Token> token_list;
 } ScanResult;
 
 class Scanner {
@@ -19,15 +17,15 @@ private:
   size_t current_pos;
   int start;
   int current_line;
-  string source;
-  vector<Token> token_list;
+  std::string source;
+  std::vector<Token> token_list;
 
 public:
-  Scanner(string s);
-  Result<vector<Token>> scan_tokens();
+  Scanner(std::string s);
+  Result<std::vector<Token>> scan_tokens();
   Result<Void> scan_token();
   void add_token(Token::Type type);
-  void add_token(Token::Type type, string literal);
+  void add_token(Token::Type type, std::string literal);
   char advance();
   void identifier();
   void number();
@@ -39,6 +37,6 @@ public:
   bool is_alpha(char c);
   bool is_alphanumeric(char c);
   bool is_at_end(void);
-  void report(string message);
-  void report(string where, string message);
+  void report(std::string message);
+  void report(std::string where, std::string message);
 };
diff --git a/src/tokens.hpp b/src/tokens.hpp
index 6e3312d..1cd9b69 100644
--- a/src/tokens.hpp
+++ b/src/tokens.hpp
@@ -2,12 +2,10 @@
 
 #include <string>
 
-using namespace std;
-
 class Token {
 public:
-  string lexeme;
-  string literal;
+  std::string lexeme;
+  std::string literal;
   int line;
   enum Type {
     END_OF_FILE = 0,
@@ -51,10 +49,10 @@ public:
     WHILE = 38,
   } tokentype;
 
-  string as_string();
+  std::string as_string();
 
   Token(Token::Type _tokentype, std::string _lexeme, std::string _literal,
         int line);
 };
 
-string token_name(Token::Type tokentype);
+std::string token_name(Token::Type tokentype);