Programming paradigm-functional programming

Speaking from a topic

 

Topic: Read in a text file, determine the frequency of use of all words and sort them from high to low, and print out a sorted list of all words and their frequencies.

 

Traditional solution

 

Functional solution

The difference between imperative and functional

1. Imperative programming style often forces us to interweave different tasks for performance reasons so that we can complete multiple tasks with one loop. In the object-oriented imperative programming language, the unit of reuse is the message used for communication between classes and classes, such as methods.

    

2. Functional programming uses map() and filter() to liberate us, allowing us to consider problems at a higher level of abstraction and see the problems more clearly. The idea of ​​reuse in functional programming languages ​​is very different.

    

   Functional languages ​​advocate the use of highly optimized operations for these data structures on a limited number of key data structures (such as list, set, and map) to form a basic operating mechanism. The developer then inserts his own data structure and high-level functions to adjust the operation mode of the mechanism according to the specific purpose.

    

    

One more question

Topic: Find the position of the first character in a character array in a string. For example, "Hello, World", ["a", "e", "i", "o", "u"], then e is the first character in the string, the position is 1, and 1 is returned

Problem-solving code:

        let words = "h e l l o w o r l d"
        let compare = ["a", "e", "i", "o", "u"]
        let wordsList = words.split(separator: " ")
        var index = 0
        zip(wordsList, compare).filter { $0 == $1}.map { (sub, str) in
            index = wordsList.firstIndex(of: sub) ?? 0
        }
        print(index)

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