本文简要介绍rust语言中 core::iter::Iterator.find_map 的用法。用法fn find_map<B, F>(&mut self, f: F) -> Option<B> where Self: Sized, F: FnMut(Self::Item) -> Option<B>, 将函数应用于迭代器的元素并返回第一个非无结果。 iter.find_map(f) 等价于 iter.filter_map(f).next()。
const result = a.map(expensiveFunction).find(x => x > 100); console.log(result); 但这在我想避免的所有元素上运行 expensiveFunction 。在上述情况下,我们应该避免运行 expensiveFunction(4)。有些语言有 find_map (例如 Rust),我没有在 lodash 和下划线中找到它。原文由 jeanpaul62 发布,翻译遵循 CC ...
(例如,Rust),我在 lodash 或下划线中都没有找到它。javascript lazy-evaluation 11个回答 20投票 内置 map 是贪婪的,所以你必须编写自己的惰性版本: const a = [2, 5, 78, 4]; const expensiveFunction = n => { console.log('expensiveFunction for', n); return 2 * n }; function *map(a, ...
I'm a Rust beginner trying to write some code which uses a HashMap. As per this documentation, I have this line: use std::hashmap::HashMap; And I get this error message when trying to compile: $ rustc -v rustc 0.11.0-pre (0ee6a8e 2014-06...
unordered_map find函数 只能找键值等于 key的元素是否存在,如果存在返回一个指向该元素的迭代器,如果不存在返回unordered_map :: end()的下一个元素
// Rust program to find the length of HashMapusestd::collections::HashMap;fnmain() {letmutmap=HashMap::new(); map.insert("Key1",101); map.insert("Key2",102); map.insert("Key3",103); map.insert("Key4",104); println!("Length of HashMap: {}\n",map.len()); println!("Ha...
如果查找失败,则返回end()函数所在的迭代器,因此用是否等于end来判断是否查找成功。 程序示例: #include<iostream>#include<string>#include<map>usingnamespacestd;intmain() { map<string,int>m; m.insert(pair<string,int>("Hello",1)); m.insert(pair<string,int>("world",2)); ...
Add find_mut_equiv function to std::collections::hashmap::HashMap #15389 Closed Bastacyclop wants to merge 2 commits into rust-lang:master from Bastacyclop:master +13 −0 Conversation 2 Commits 2 Checks 0 Files changed 1 Conversation Bastacyclop commented Jul 3, 2014 I needed this ...
#include<iostream>#include<map>using std::cin;using std::cout;using std::endl;using std::map;using std::string;intmain(){std::map<string,string>m1={{"h","htop"},{"k","ktop"},{"t","ttop"},{"r","rtop"},{"w","wtop"},{"p","ptop"},};string key="h";autoitem=m1....
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