slice

问题 I'd like to write some code like below struct SomeData(u8, u8); impl SomeData { fn to_bytes(&self) -> &[u8] { let mut bytes: [u8; 16] = [0; 16]; // fill up buffer with some data in `SomeData`. bytes[0] = self.0; bytes[1] = self.1; // return slice &bytes[..] } } I know the reason why above code doesn't work. How can I return a reference specifying that its lifetime is the same as self ? 回答1: Explicit lifetime annotation of a reference cannot extend lifetime of an object it refers to. bytes is

问题 I'd like to write some code like below struct SomeData(u8, u8); impl SomeData { fn to_bytes(&self) -> &[u8] { let mut bytes: [u8; 16] = [0; 16]; // fill up buffer with some data in `SomeData`. bytes[0] = self.0; bytes[1] = self.1; // return slice &bytes[..] } } I know the reason why above code doesn't work. How can I return a reference specifying that its lifetime is the same as self ? 回答1: Explicit lifetime annotation of a reference cannot extend lifetime of an object it refers to. bytes is

问题 I use the dataset from UCI repo: http://archive.ics.uci.edu/ml/datasets/Energy+efficiency Then doing next: from pandas import * from sklearn.neighbors import KNeighborsRegressor from sklearn.linear_model import LinearRegression, LogisticRegression from sklearn.svm import SVR from sklearn.ensemble import RandomForestRegressor from sklearn.metrics import r2_score from sklearn.cross_validation import train_test_split dataset = read_excel('/Users/Half_Pint_boy/Desktop/ENB2012_data.xlsx') dataset

问题 I have a numpy array A and I want to modify values in it using a indexing list B. But the thing is in my slicing I can have an element of the array multiple times... This example will explain better what I mean by that : import numpy as np A = np.arange(5) + 0.5 B = np.array([0, 1, 0, 2, 0, 3, 0, 4]) print A[B] returns as expected [ 0.5 1.5 0.5 2.5 0.5 3.5 0.5 4.5] . However if I do that : A[B] += 1. print A I was expecting to obtain [ 4.5 2.5 3.5 4.5 5.5] as the first element is repeated 4

问题 I want to unmarshal a string that contains JSON, however the Unmarshal function takes a []byte as input. How can I convert my UTF8 string to []byte ? 回答1: This question is a possible duplicate of How to assign string to bytes array, but still answering it as there is a better, alternative solution: Converting from string to []byte is allowed by the spec, using a simple conversion: Conversions to and from a string type [...] Converting a value of a string type to a slice of bytes type yields a

问题 Go Slice question, please check below and comment if I am missing something. import "fmt" func main() { s := []int{2, 3, 5, 7, 11, 13} s = s[1:] fmt.Println(s) s = s[2:] fmt.Println(s) s = s[5:] fmt.Println(s) } Output: [3 5 7 11 13] [7 11 13] panic: runtime error: slice bounds out of range The above makes sense. func main() { s := []int{2, 3, 5, 7, 11, 13} s = s[:1] fmt.Println(s) s = s[:2] fmt.Println(s) s = s[:5] fmt.Println(s) } Output: [2] [2 3] [2 3 5 7 11] Should this also get array

问题 I'm have a function, below, that is comparing the text in two selectors. If the last occurrence of both of these selectors is the same, the "next" button will disappear. Currently, this is not working. I'm not sure why this is happening. Just fyi, what I'm trying to select is a schema 'itemprop' and is somewhat atypical. Here is the fiddle - https://jsfiddle.net/carbot3000/8qjdxsz7/3/ function showHide(){ if ( $('#areall span[itemprop="reviewBody"]').last().text().trim() == $('.review span

问题 I have a number of timeseries data in arrays and wish to extract values between given dates in the simplest way possible avoiding loops. Here's an example: from numpy import * from datetime import * # datetime array date_a=array([ datetime(2000,1,1), datetime(2000,1,2), datetime(2000,1,3), datetime(2000,1,4), datetime(2000,1,5), ]) # item array, indices corresponding to datetime array item_a=array([1,2,3,4,5]) # extract items in a certain date range # after a certain date, works fine item_b

问题 I have an array containing data (ID numbers and data associated with them). The number of items in the array is always variable and not known. I want to split this array in two equal parts IF there's more than 2 items in the original array (not the slice). Then I want to create two indipendent UL lists containing the resulting array slices items. If the total number of items in the original array is odd, the first list should carry one more item. I came up with this, but I'm sure I'm doing it

问题 This is a pretty straightforward question: If the capacity of a slice in Golang can be exceeded, why is there a capacity parameter in the first place? I reckon this has to do with the memory management , some kind of "knowing where to allocate the slice in memory" but I don't know exactly. 回答1: If the capacity of a slice in Golang can be exceeded, why is there a capacity parameter in the first place? I don't know what you mean by this, but the capacity can't be exceeded. Slices can be indexed