是否所有的一类属性常量需要有成员函数声明为const呢？ [英] Does a class with all attributes const need to have member function declared const as well?

问题描述

标题已经说明了一切。让我扩大一点不过：我类，其所有属性常量：

The title already says all. Let me expand a little nevertheless: I've class whose all attributes are const:

template< class perm  = Perm16 >
class PermutationGroup {
public:
  using StrongGeneratingSet = std::vector< std::vector< perm > >;

  const std::string name;
  const uint64_t N;
  const StrongGeneratingSet sgs;
  PermutationGroup(std::string name, uint64_t N, StrongGeneratingSet sgs) :
      name(name), N(N), sgs(sgs) { assert(check_sgs()); };

  bool check_sgs() const;            // defined as const
  bool is_canonical(vect v) const;   // defined as const

  [...]

};

这是任何使用定义所有成员函数作为常量为好？还是我不必要地重复自己？

Is it of any use to define all member function as const as well ? Or am I needlessly repeating myself ?

推荐答案

如果你不申报的成员函数的常量的，你不能调用他们的常量的通过的 const引用引用的对象或对象的。例如，以下将不起作用：

If you do not declare the member functions as const, you can't invoke them on const objects or objects referenced by a const reference. For example, the following won't work:

const PermutationGroup& group = PermutationGroup("foobar", 42, ...);
group.check_sgs(); // ERROR: can't invoke non-const function on const objects

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