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Generate random number between two numbers in JavaScript
Is there a way to generate a random number in a specified range (e.g. from 1 to 6: 1, 2, 3, 4, 5, or 6) in JavaScript?
23 A...
What is Weak Head Normal Form?
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These expressions are all in normal form:
42
(2, "hello")
\x -> (x + 1)
These expressions are not in normal form:
1 + 2 -- we could evaluate this to 3
(\x -> x + 1) 2 -- we could apply the function
"he" ++ "llo" -- we could apply the (++)
(1 + 1, 2 + 2) ...
How do I find a “gap” in running counter with SQL?
...gap" in a counter column in an SQL table. For example, if there are values 1,2,4 and 5 I'd like to find out 3.
20 Answers
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C++常用排序算法汇总 - C/C++ - 清泛网 - 专注C/C++及内核技术
...堆排序(HeapSort)，插入排序(InsertSort)，希尔排序(ShellSort) 1、选择排序(SelectSort)
/************************************
* 简单选择排序
* 稳定排序，O{n^2} ~ O{n^2}
* 从首位开始，循环一次找出一个比首位小的值，交换
*
* https://www.tsi...
Why do Lua arrays(tables) start at 1 instead of 0?
...ionale behind the decision of this part of Lua. Why does indexing start at 1? I have read (as many others did) this great paper . It seems to me a strange corner of a language that is very pleasant to learn and program. Don't get me wrong, Lua is just great but there has to be an explanation somewh...
项目管理实践教程一、工欲善其事，必先利其器【Basic Tools】 - 项目管理 -...
...首先安装一些必须的软件，主要有下面的4个，其中软件1和2使用在服务器机上，软件3和4安装在客户端机上。另外，我们还有用到MSBui 今天，我们首先安装一些必须的软件，主要有下面的4个，其中软件1和2使用在服务器机上，...
How can I setup & run PhantomJS on Ubuntu?
...ntomJS and recorded it to video: https://www.dailymotion.com/video/xnizmh_1_webcam
25 Answers
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Can dplyr package be used for conditional mutating?
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Use ifelse
df %>%
mutate(g = ifelse(a == 2 | a == 5 | a == 7 | (a == 1 & b == 4), 2,
ifelse(a == 0 | a == 1 | a == 4 | a == 3 | c == 4, 3, NA)))
Added - if_else: Note that in dplyr 0.5 there is an if_else function defined so an alternative would be to replace ifelse with i...
How to show all shared libraries used by executables in Linux?
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13 Answers
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Dynamically select data frame columns using $ and a character value
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185
You can't do that kind of subsetting with $. In the source code (R/src/main/subset.c) it state...