diff --git a/language/pl0/pl0.cc b/language/pl0/pl0.cc
index 8ce8896..221d3e5 100644
--- a/language/pl0/pl0.cc
+++ b/language/pl0/pl0.cc
@@ -63,19 +63,6 @@ string format_error_message(const string& path, size_t ln, size_t col, const str
     return ss.str();
 }
 
-bool read_file(const char* path, vector<char>& buff)
-{
-    ifstream ifs(path, ios::in | ios::binary);
-    if (ifs.fail()) {
-        return false;
-    }
-    buff.resize(static_cast<unsigned int>(ifs.seekg(0, ios::end).tellg()));
-    if (!buff.empty()) {
-        ifs.seekg(0, ios::beg).read(&buff[0], static_cast<streamsize>(buff.size()));
-    }
-    return true;
-}
-
 /*
  * Ast
  */
@@ -96,23 +83,20 @@ struct SymbolScope
     SymbolScope(shared_ptr<SymbolScope> outer) : outer(outer) {}
 
     bool has_symbol(const string& ident) const {
-        auto ret = constants.find(ident) != constants.end() || variables.find(ident) != variables.end();
+        auto ret = constants.count(ident) || variables.count(ident);
         return ret ? true : (outer ? outer->has_symbol(ident) : false);
     }
 
     bool has_constant(const string& ident) const {
-        auto ret = constants.find(ident) != constants.end();
-        return ret ? true : (outer ? outer->has_constant(ident) : false);
+        return constants.count(ident) ? true : (outer ? outer->has_constant(ident) : false);
     }
 
     bool has_variable(const string& ident) const {
-        auto ret = variables.find(ident) != variables.end();
-        return ret ? true : (outer ? outer->has_variable(ident) : false);
+        return variables.count(ident) ? true : (outer ? outer->has_variable(ident) : false);
     }
 
     bool has_procedure(const string& ident) const {
-        auto ret = procedures.find(ident) != procedures.end();
-        return ret ? true : (outer ? outer->has_procedure(ident) : false);
+        return procedures.count(ident) ? true : (outer ? outer->has_procedure(ident) : false);
     }
 
     map<string, int>                constants;
@@ -225,14 +209,14 @@ struct Environment
         auto it = scope->constants.find(ident);
         if (it != scope->constants.end()) {
             return it->second;
-        } else if (scope->variables.find(ident) != scope->variables.end()) {
+        } else if (scope->variables.count(ident)) {
             return variables.at(ident);
         }
         return outer->get_value(ident);
     }
 
     void set_variable(const string& ident, int val) {
-        if (scope->variables.find(ident) != scope->variables.end()) {
+        if (scope->variables.count(ident)) {
             variables[ident] = val;
         } else {
             outer->set_variable(ident, val);
@@ -431,10 +415,16 @@ int main(int argc, const char** argv)
     // Read a source file into memory
     auto path = argv[1];
     vector<char> source;
-    if (!read_file(path, source)) {
+
+    ifstream ifs(path, ios::in | ios::binary);
+    if (ifs.fail()) {
         cerr << "can't open the source file." << endl;
         return -1;
     }
+    source.resize(static_cast<unsigned int>(ifs.seekg(0, ios::end).tellg()));
+    if (!source.empty()) {
+        ifs.seekg(0, ios::beg).read(&source[0], static_cast<streamsize>(source.size()));
+    }
 
     // Setup a PEG parser
     peg parser(grammar);
diff --git a/peglib.h b/peglib.h
index 67cd13c..5d6702d 100644
--- a/peglib.h
+++ b/peglib.h
@@ -1313,7 +1313,7 @@ inline void DefinitionReference::accept(Visitor& v) { v.visit(*this); }
 
 inline void AssignIDToDefinition::visit(Holder& ope) {
     auto p = (void*)ope.outer_;
-    if (ids.find(p) != ids.end()) {
+    if (ids.count(p)) {
         return;
     }
     auto id = ids.size();
@@ -1554,7 +1554,7 @@ private:
         void visit(DefinitionReference& ope) override {
             if (ope.name_ == name_) {
                 s_ = ope.s_;
-            } else if (refs_.find(ope.name_) != refs_.end()) {
+            } else if (refs_.count(ope.name_)) {
                 ;
             } else {
                 refs_.insert(ope.name_);
@@ -1645,7 +1645,7 @@ private:
             auto ope = sv[baseId + 2].get<std::shared_ptr<Ope>>();
 
             auto& grammar = *data.grammar;
-            if (grammar.find(name) == grammar.end()) {
+            if (!grammar.count(name)) {
                 auto& rule = grammar[name];
                 rule <= ope;
                 rule.name = name;
@@ -1729,7 +1729,7 @@ private:
 
                     const auto& ident = sv[baseId].get<std::string>();
 
-                    if (data.references.find(ident) == data.references.end()) {
+                    if (!data.references.count(ident)) {
                         data.references[ident] = sv.s; // for error handling
                     }
 
@@ -1835,7 +1835,7 @@ private:
         for (const auto& x : data.references) {
             const auto& name = x.first;
             auto ptr = x.second;
-            if (grammar.find(name) == grammar.end()) {
+            if (!grammar.count(name)) {
                 if (log) {
                     auto line = line_info(s, ptr);
                     log(line.first, line.second, "'" + name + "' is not defined.");