reduce

问题 I have the following list of tuples: [('a', 1), ('a', 1), ('b', 1), ('c',1), ('a', 1), ('c', 1)] I would like to know if I can utilize python's reduce function to aggregate them and produce the following output : [('a', 3), ('b', 1), ('c', 2)] Or if there are other ways, I would like to know as well (loop is fine) 回答1: It seems difficult to achieve using reduce , because if both tuples that you "reduce" don't bear the same letter, you cannot compute the result. How to reduce ('a',1) and ('b'

问题 I have the following list of tuples: [('a', 1), ('a', 1), ('b', 1), ('c',1), ('a', 1), ('c', 1)] I would like to know if I can utilize python's reduce function to aggregate them and produce the following output : [('a', 3), ('b', 1), ('c', 2)] Or if there are other ways, I would like to know as well (loop is fine) 回答1: It seems difficult to achieve using reduce , because if both tuples that you "reduce" don't bear the same letter, you cannot compute the result. How to reduce ('a',1) and ('b'

问题 I have the following list of tuples: [('a', 1), ('a', 1), ('b', 1), ('c',1), ('a', 1), ('c', 1)] I would like to know if I can utilize python's reduce function to aggregate them and produce the following output : [('a', 3), ('b', 1), ('c', 2)] Or if there are other ways, I would like to know as well (loop is fine) 回答1: It seems difficult to achieve using reduce , because if both tuples that you "reduce" don't bear the same letter, you cannot compute the result. How to reduce ('a',1) and ('b'

问题 I have the following list of tuples: [('a', 1), ('a', 1), ('b', 1), ('c',1), ('a', 1), ('c', 1)] I would like to know if I can utilize python's reduce function to aggregate them and produce the following output : [('a', 3), ('b', 1), ('c', 2)] Or if there are other ways, I would like to know as well (loop is fine) 回答1: It seems difficult to achieve using reduce , because if both tuples that you "reduce" don't bear the same letter, you cannot compute the result. How to reduce ('a',1) and ('b'

问题 Fold (aka reduce ) is considered a very important higher order function. Map can be expressed in terms of fold (see here). But it sounds more academical than practical to me. A typical use could be to get the sum, or product, or maximum of numbers, but these functions usually accept any number of arguments. So why write (fold + 0 '(2 3 5)) when (+ 2 3 5) works fine. My question is, in what situation is it easiest or most natural to use fold ? 回答1: The point of fold is that it's more abstract.

问题 Fold (aka reduce ) is considered a very important higher order function. Map can be expressed in terms of fold (see here). But it sounds more academical than practical to me. A typical use could be to get the sum, or product, or maximum of numbers, but these functions usually accept any number of arguments. So why write (fold + 0 '(2 3 5)) when (+ 2 3 5) works fine. My question is, in what situation is it easiest or most natural to use fold ? 回答1: The point of fold is that it's more abstract.

问题 I have a function that finds the longest word in a string. function findLongestWord(str) { var longest = str.split(' ').reduce((longestWord, currentWord) =>{ return currentWord.length > longestWord.length ? currentWord : longestWord; }, ""); return longest; } console.log(findLongestWord("The quick brown fox jumped over the lazy dog")); I'm having a hard time converting this to find the shortest word. Why can't I just change currentWord.length > longestWord.length to currentWord.length <

问题 I have a function that finds the longest word in a string. function findLongestWord(str) { var longest = str.split(' ').reduce((longestWord, currentWord) =>{ return currentWord.length > longestWord.length ? currentWord : longestWord; }, ""); return longest; } console.log(findLongestWord("The quick brown fox jumped over the lazy dog")); I'm having a hard time converting this to find the shortest word. Why can't I just change currentWord.length > longestWord.length to currentWord.length <

问题 I have a function that finds the longest word in a string. function findLongestWord(str) { var longest = str.split(' ').reduce((longestWord, currentWord) =>{ return currentWord.length > longestWord.length ? currentWord : longestWord; }, ""); return longest; } console.log(findLongestWord("The quick brown fox jumped over the lazy dog")); I'm having a hard time converting this to find the shortest word. Why can't I just change currentWord.length > longestWord.length to currentWord.length <

问题 I have a function that finds the longest word in a string. function findLongestWord(str) { var longest = str.split(' ').reduce((longestWord, currentWord) =>{ return currentWord.length > longestWord.length ? currentWord : longestWord; }, ""); return longest; } console.log(findLongestWord("The quick brown fox jumped over the lazy dog")); I'm having a hard time converting this to find the shortest word. Why can't I just change currentWord.length > longestWord.length to currentWord.length <