clause 02: Replace # define as const,enum,inline as possible

I. Overview

Minimize the use of preprocessor-macro substitution

Second, details

1. Constants for macro substitution

Old version: #define N 10;

New version: const int n = 10;

Comparison: #define不被视为语言的一部分, the tick name n is removed by the preprocessor before the compiler starts processing the source code.

Supplement: class's exclusive constants require encapsulation, and # define does not provide encapsulation (it does not value scopes).

2. Macros that resemble functions

Older version: #define CALL_WITH_MAX (A, B) f ((a) > (b)? (a): (b))

New version: Template<typename t> inline void Callwithmax (const t &a, const T &b) {f (a > B? a:b);}

Comparison: In older versions, there is a lot of constraint and complexity in invoking arguments, while inline is similar in efficiency but easy in form and error-prone.

Add: Callwithmax is a real function that adheres to scopes and access rules, and you can't write a class's private member function with a macro.

3. Enum has a const member, so it can be used as a constant expression

clause 02: Replace # define as const,enum,inline as possible