1141_ SiCp learning notes_ Functions abstracted as black boxes

    All learning summary ：GitHub - GreyZhang/g_SICP: learn SICP and hack lisp.

    First of all, notice , The previous repeated process of solving the square root is actually a recursive process . The design of a program depends on its own function , In the process of execution, we need to constantly make self Owen calls . Actually , This way makes me feel a little bit like feedback adjustment . Another point is that the process of solving this square root is actually a combination of a series of functions , This is also the same description as the overall to local design I thought of earlier .

    Here is a clarification that is of great reference significance , Several functions are used to calculate the square root in front of the design . The design of software is actually to divide a function into several . however , The key point of this decomposition strategy is not to split a function into different functions , After all, if you force a split , A function can be split into ten lines , A large program can be divided into several functions . Such significance is not great . The premise of splitting should be that the disassembled function can become an independent module that can be reused constantly . Another point is that , The design application of this black box is likely to be used in the overall description stage considered in the previous learning process . At this stage , We can assume the existence of some functions without thinking too much about the way they are implemented . The design of function modules can hide details , This also brings another point of thinking ： If you use C Language for similar design , In fact, try to avoid using global variables to interact between different functions . Or say , Try not to use the same variable for different functions , Otherwise, the coupling of functions will be enhanced . It is not easy to consider some function calls as black boxes in the understanding of software .

    Although the title of this part is called local name , But it has nothing to do with local variables . Here we mainly talk about the relationship between formal parameters and arguments , Rather than the expression of local quantities . And formal parameters , Only when there is corresponding information bound with it can a scope play its corresponding role .

    The initial program implementation was a set of functions , There may be conflict problems with commonly used functions . such as , A good enough method may be used in many ways , But the content of judgment is different . such , There may be conflicts when designing different software functions . And the above gives a non conflicting way , That is to make these contents into sub functions of functions . such , Its scope is also limited to the interior of a function .

    further , Because each function uses the same parameters . Therefore, the design here can directly omit a parameter , Use the same parameters directly . This design is indeed a lot simpler , But I want to come here C It may still be difficult to implement in the design of language . however , Either of the latter two implementations , In fact, it further hides the details of the design , Make the whole function design more black box .