Unordered_set with closure as a hash function

Grzegorz Jabłoński
1 parent f107c09e
Showing 3 changed files with 57 additions and 2 deletions
examples09/07-closures/employee.h
examples09/07-closures/makefile
examples09/07-closures/unordered_set3.cpp
+#ifndef __EMPLOYEE_H__
+#define __EMPLOYEE_H__
+#include <string>
+#include <iostream>
+
+struct Employee
+{
+  std::string FirstName, LastName, ID;
+  Employee (const std::string & fn, const std::string & ln,
+	    const std::string & I):FirstName (fn), LastName (ln), ID (I)
+  {
+  };
+  friend std::ostream& operator<< (std::ostream & o, const Employee & e)
+  {
+    o << e.FirstName << " " << e.LastName << " " << e.ID;
+    return o;
+  };
+
+  bool operator==(const Employee& o) const
+  {
+    return (FirstName == o.FirstName) && (LastName == o.LastName) && (ID == o.ID);
+  }
+};
+#endif	/* __EMPLOYEE_H__ */
-all: fun1 fun2 fun3 fun4 fun5
+all: fun1 fun2 fun3 fun4 fun5 unordered_set3
 fun1: fun1.o
 	g++ -g -Wall $^ -o $@
@@ -30,7 +30,14 @@ fun5.o: fun5.cpp
 fun5: fun5.o
 	g++ -g -Wall $^ -o $@
+
+unordered_set3.o: unordered_set3.cpp
+	g++ -std=c++2a -g -c -Wall $< -o $@
+
+unordered_set3: unordered_set3.o
+	g++ -g -Wall $^ -o $@
+
 .PHONY: clean
 clean:
-	-rm fun1.o fun1 fun2.o fun2 fun3.o fun3 fun4.o fun4 fun5.o fun5
 \ No newline at end of file
+	-rm fun1.o fun1 fun2.o fun2 fun3.o fun3 fun4.o fun4 fun5.o fun5 unordered_set3.o unordered_set3
 \ No newline at end of file
+#include <functional>
+#include <unordered_set>
+using namespace std;
+#include "employee.h"
+
+int main() {
+  Employee Ben("Ben", "Keller", "000-00-0000");
+  Employee Bill("Bill", "McQuain", "111-11-1111");
+  Employee Dwight("Dwight", "Barnette", "888-88-8888");
+
+  auto empHash = [](const Employee &o) {
+    return std::hash<std::string>()(o.FirstName) ^
+           (std::hash<std::string>()(o.LastName) << 1) ^
+           (std::hash<std::string>()(o.ID) << 2);
+  };
+
+  unordered_set<Employee, decltype(empHash)> S;
+  S.insert(Bill);
+  S.insert(Dwight);
+  S.insert(Ben);
+
+  for (auto i : S)
+    cout << i << endl;
+}