What are side effects of clojure)

What are side effects of clojure ):

Pure function: the input and output data streams are all explicit. Function data exchange only involves parameters and return values.
Implicit (implicit) function: A function can exchange data with the outside world in a way other than parameters and return values. Eg: modify global variables and use I/O to read/output files and print them to the screen.

For example, open is a function used to open a file. It opens a file and you can perform operations on the file, such as open ('C:/test.txt '), the return value of this statement is 1 or-1 (whether the file exists). This function is used, and its side effect is to open a file.