# ECE 522 Assignment 5: Refactoring solution

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Question 1: Consider the following code: pub struct L{ x: usize, y: usize, } pub fn foo (text: &str, string: &str)->Vec { let mut r= Vec::new(); let mut x=0; for line in text.lines(){ for (y, _) in line.match_indices(string){ r.push(L{ x : x, y: y, }) } x+=1; } r } a- What does this program do? b- Try running the Foo function with the following code and report the output. let results = foo(“Shall I compare thee to a summer’s day? Thou art more lovely and more temperate: Rough winds do shake the darling buds of May, And summer’s lease hath all too short a date: Sometimes too hot the eye of heaven shines, And too often is his gold complexion dimm’d: And every fair from fair sometimes declines, By chance or natures changing course untrimm’d; By thy eternal summer shall not fade, Nor lose possession of that fair thou owest; Nor shall Death brag thou wander’st in his shade, When in eternal lines to time thou growest: So long as men can breathe or eyes can see, So long lives this and this gives life to thee.”, “the”); for x in results {println!(“x : {}, y : {}”, x.x, x.y);} Question 2: Convert the foo function to the functional style by applying the following refactorings: a- Apply iterators to replace the need to manually track y at line 9. 1 ECE 522 | Software Construction, Verification and Evolution b- Use the map function to replace the need to manually update the r vectors. c- Keep adding iterators until the for loops and let statements (in function foo) disappear. Question 3: Consider the following code: use std::collections::HashMap; #[derive(Debug)] struct TrieNode { chs: HashMap<char, TrieNode>, value: Option, } #[derive(Debug)] struct Trie { root: TrieNode, } impl Trie { fn new() -> Trie { Trie { root: TrieNode { chs: HashMap::new(), value: None, }, } } fn add_string(&mut self, string: String, value: i32) { let mut current_node = &mut self.root; for c in string.chars() { current_node = current_node.chs .entry(c) .or_insert(TrieNode { chs: HashMap::new(), value: None, }); } current_node.value = Some(value); } } fn main() { let mut trie = Trie::new(); 2 ECE 522 | Software Construction, Verification and Evolution trie.add_string(“B”.to_string(), 1); trie.add_string(“Bar”.to_string(), 2); println!(“{:#?}”, trie); } The above code implements a Trie (https://docs.rs/radix_trie/0.0.9/radix_trie/struct.Trie.html#method.len) which is a data-structure for storing and querying string-like keys and associated values. a- Add your own implementation for length(&self)->usize that returns the number of elements stored in the trie. b- Add your own implementation for iter(&self) -> Vec<(char, Option)> which returns an iterator over the keys and values of the Trie. c- Add your own implementation for find(&self, key: &String) -> Option<&TrieNode> which searches the Trie for a given key and returns a reference to that key’s corresponding node if found. d- Add your own implementation for delete(&mut self, key: &String) -> Option to remove a key (from a Trie) and returns the value corresponding to that key. 3