by | constexpr | const |
| If a member function is declared as constexpr then it will be treated as const as well. | If a member function is declared as const then it will not be treated as constexpr. |
| If a variable is declared as constexpr then it will be treated as const as well. | If a variable is declared as const then it will not be treated as constexpr. |
| constexpr is mainly used for optimization purpose where computation can be done at compile level to optimize run time performance. | However const is mainly used to ensure that there are no accidental changes done by the member method to member data. |
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