High quality subroutine

High quality subroutines

The meaning of subroutines ：

• Reduce duplicate code , Make the whole code not bloated
• Improve code efficiency , Local function improvement subroutine
• Promote the development of modern programming

Reason for creating subroutines ：

• Reduce complexity . You can use subroutines to hide some information , Reduce code size , Improve correctness, etc

• Introduce the middle 、 Intelligible abstraction . According to good naming , It can be well-known

• Avoid code duplication . Improve the consistency of the same function code

• Subclassing is supported . Reduce the chance of making mistakes

• Hide order . Subroutines are independent of each other , There is no sequence limit for development

• Hide pointer operation . Concentrate on the main intention

• Improve portability . Distinguish between non portable code , Reduce the workload of cutting and transplantation

• Simplify complex Boolean judgments . Make the main process clearer

• improve performance . By modifying the performance of a subroutine , It can improve the performance of the whole program

• The length of the subroutine depends on the actual situation

  … …

• Easy to reconstruct

Subroutine design ：

• Functional cohesion . Embodied in the principle of single responsibility , Each subroutine does only one thing , More reliable

Subroutine name principle ：

• Describe what subroutines do . The name should describe all the results and side effects , But not long and stupid
• Avoid using meaningless , A vague or ambiguous verb .
• Don't just use numbers to form different subroutine names .
• Determine the length of the subroutine name as needed . The best length 9 – 15 Characters
• When naming a function, you should describe the return value .
• When naming a process, use a strong verb object structure .
• Use antithetical words accurately .
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• Establish naming rules for common operations .

How long can a subroutine be written

• According to nesting , level , Depending on the number of decision points and other factors

How to use subroutine parameters

• Press enter - modify - Output sequence parameters .
• Consider creating IN and OUT keyword .
• If several subroutines are used for similar parameters , There should be consistency .
• Do not have parameters that cannot be used .
• Put the state and error variables last
• Do not use subroutine parameters for working variables
• The assumption of using parameters in the interface is explained . Use assertion
• The number of parameters is limited to 7 Within a
• Pass a variable or object to a subroutine to maintain its interface abstraction
• Use named parameters
• Ensure that the actual parameters match the formal parameters

Special considerations when using functions ：

• function & The process . What has a return value is a function , What has no return value is the procedure . The return value is void Is also a process . If the main purpose of a subroutine is to return the return value specified by its name , You should return the function , Otherwise, the process should be used .

Set the return value of the return function , Suggest

• Check all possible return paths . Initialize the return value with a default value at the beginning of the function .
• Do not return references or pointers to local data .

Macro subroutines and inline subroutines

• Enclose the macro expression in parentheses

  #define Cube(a) a*a*a // error demo e.g. Cube(x+1) x+1*x+1*x+1
  #define Cube(a) (a)*(a)*(a) // error demo
  #define Cube(a) ((a)*(a)*(a)) // right demo
  

• Enclose macros with multiple statements in curly braces . Replacing function calls with macros is risky , And it's not easy to understand , Unless necessary , It is recommended to avoid using this method .

• Use the method of naming subroutines to name macros whose code is like subroutines after expansion , In order to replace macros with subroutines when necessary .

  • The side effect is ++ and – Operator , It is easy to mistake macros for subroutines

Restrictions on the use of macro subroutines ,C++

• const Can be used to define constants
• inline Define embedded code
• template Define various standard operations in a type safe manner
• enum Can be used to define enumeration types
• typedef Used to define simple type substitution
• Try not to use macros instead of subroutines , Because it is difficult to find problems with the debugger

Inline subroutine

• inline keyword , Use sparingly