support bazel complie this project and format code.

practical_exercises/10_day_practice/day4/const/BUILD

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+# please run `bazel run //practical_exercises/10_day_practice/day4/const:obj_func`
+# please run `bazel run //practical_exercises/10_day_practice/day4/const:obj_ref`
+
+load("@rules_cc//cc:defs.bzl", "cc_binary")
+
+cc_binary(
+    name = "obj_func",
+    srcs = ["obj_func.cpp"],
+)
+cc_binary(
+    name = "obj_ref",
+    srcs = ["obj_ref.cpp"],
+)

practical_exercises/10_day_practice/day4/const/obj_func.cpp

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+#include <iostream>
+using namespace std;
+class R {
+public:
+  R(int r1, int r2) {
+    R1 = r1;
+    R2 = r2;
+  }
+  // const区分成员重载函数
+  void print();
+  void print() const;
+
+private:
+  int R1, R2;
+};
+/*
+常成员函数说明格式：类型说明符  函数名（参数表）const;
+这里，const是函数类型的一个组成部分，因此在实现部分也要带const关键字。
+const关键字可以被用于参与对重载函数的区分
+通过常对象只能调用它的常成员函数
+*/
+
+void R::print() {
+  cout << "普通调用" << endl;
+  cout << R1 << ":" << R2 << endl;
+}
+//实例化也需要带上
+void R::print() const {
+  cout << "常对象调用" << endl;
+  cout << R1 << ";" << R2 << endl;
+}
+int main() {
+  R a(5, 4);
+  a.print(); //调用void print()
+  //通过常对象只能调用它的常成员函数
+  const R b(20, 52);
+  b.print(); //调用void print() const
+  
+  return 0;
+}

practical_exercises/10_day_practice/day4/const/obj_ref.cpp

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+
+#include <iostream>
+using namespace std;
+void display(const double &r);
+
+class A {
+public:
+  A(int i, int j) {
+    x = i;
+    y = j;
+  }
+
+private:
+  int x, y;
+};
+int main() {
+  double d(9.5);
+  display(d);
+  A const a(3, 4); // a是常对象，不能被更新
+  
+  return 0;
+}
+void display(const double &r)
+//常引用做形参，在函数中不能更新 r所引用的对象。
+{
+  cout << r << endl;
+}

practical_exercises/10_day_practice/day4/const/readme.md

@@ -0,0 +1,8 @@
+<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵Ķ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>г<EFBFBD>ʼ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҳ<EFBFBD><EFBFBD>ܱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>¡<EFBFBD>
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+const  <20><><EFBFBD><EFBFBD>˵<EFBFBD><CBB5><EFBFBD><EFBFBD>  &<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
+<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>󣺱<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>г<EFBFBD>ʼ<EFBFBD><EFBFBD>,<2C><><EFBFBD>ܱ<EFBFBD><DCB1><EFBFBD><EFBFBD>¡<EFBFBD>
+<EFBFBD><EFBFBD><EFBFBD><EFBFBD>  const  <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
+<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>飺<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ԫ<EFBFBD>ز<EFBFBD><EFBFBD>ܱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>¡<EFBFBD>
+<EFBFBD><EFBFBD><EFBFBD><EFBFBD>˵<EFBFBD><EFBFBD><EFBFBD><EFBFBD>  const  <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>[<5B><>С]...
+<EFBFBD><EFBFBD>ָ<EFBFBD>룺ָ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD>롣