conditional

Best way to combine a permutation of conditional statements

由 纵饮孤独 提交于 2020-02-28 04:25:18
问题 So, I have a series of actions to perform, based on 4 conditional variables - lets say x,y,z & t. Each of these variables have a possible True or False value. So, that is a total of 16 possible permutations. And I need to perform a different action for each permutation. What is the best way to do this rather than making a huge if-else construct. Lets see a simplified example. This is how my code would look if I try to contain all the different permutations into a large if-else construct. if

Best way to combine a permutation of conditional statements

由 独自空忆成欢 提交于 2020-02-28 04:22:33
问题 So, I have a series of actions to perform, based on 4 conditional variables - lets say x,y,z & t. Each of these variables have a possible True or False value. So, that is a total of 16 possible permutations. And I need to perform a different action for each permutation. What is the best way to do this rather than making a huge if-else construct. Lets see a simplified example. This is how my code would look if I try to contain all the different permutations into a large if-else construct. if

Best way to combine a permutation of conditional statements

由 谁都会走 提交于 2020-02-28 04:20:35
问题 So, I have a series of actions to perform, based on 4 conditional variables - lets say x,y,z & t. Each of these variables have a possible True or False value. So, that is a total of 16 possible permutations. And I need to perform a different action for each permutation. What is the best way to do this rather than making a huge if-else construct. Lets see a simplified example. This is how my code would look if I try to contain all the different permutations into a large if-else construct. if

R dplyr::mutate with ifelse conditioned on a global variable recycles result from first row

由 我的梦境 提交于 2020-02-25 06:10:20
问题 I am curious why an ifelse() statement within a call to dplyr::mutate() only seems to apply to the first row of my data frame. This returns a single value, which is recycled down the entire column. Since the expressions evaluated in either case of the ifelse() are only valid in the context of my data frame, I would expect the condition check and resulting expression evaluations to be performed on the columns as a whole, not just their first elements. Here's an example: I have a variable

Conditional unique constraint with multiple fields in oracle db

由 落花浮王杯 提交于 2020-02-13 08:10:18
问题 I have this table: XPTO_TABLE (id, obj_x, date_x, type_x, status_x) I wanna create a unique constraint that applies to the fields (obj_x, date_x, type_x) only when status_x <> 5 . I have tried to create this one but Oracle says: line 1: ORA-00907: missing right parenthesis CREATE UNIQUE INDEX UN_OBJ_DT_TYPE_STATUS ON XPTO_TABLE( (CASE WHEN STATUS_X <> 5 THEN (OBJ_X, TO_CHAR (DATE_X, 'dd/MM/yyyy'), TYPE_X) ELSE NULL END)); What's the correct syntax ? 回答1: @jamesfrj: it looks like you are

Spring条件注解@Conditional

由 Deadly 提交于 2020-02-06 01:00:18
@Conditional是Spring4新提供的注解，它的作用是根据某个条件创建特定的Bean，通过实现Condition接口，并重写matches接口来构造判断条件。总的来说，就是根据特定条件来控制Bean的创建行为，这样我们可以利用这个特性进行一些自动的配置。 　　本文将分为三大部分，@Conditional源码的介绍、Condition的使用示例和@Conditional的扩展注解的介绍。 一、@Conditional的源码 @Target({ElementType.TYPE, ElementType.METHOD}) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface Conditional { /** * All {@link Condition Conditions} that must {@linkplain Condition#matches match} * in order for the component to be registered. */ Class<? extends Condition>[] value(); } 从源码中可以看到，@Conditional注解可以用在类和方法上，需要传入一个实现了Condition接口class数组。 二、代码示例

Python efficiency of and vs multiple ifs

由 一笑奈何 提交于 2020-01-31 06:54:14
问题 Is there an efficiency difference between using and in an if statement and using multiple if statements? In other words, is something like if expr1 == expr2 and expr3==expr4: dostuff() different from an efficiency standpoint then: if expr1 == expr2: if expr3 == expr4: dostuff() My very basic testing does not reveal a difference, but does someone with more knowledge (or at least more thorough testing) have a definitive answer? 回答1: In either case, expr1 == expr2 evaluates to false in if , the

spring5学习系列之------3 给容器注册组件三 @Conditional 和 @Import 注解用法

由 懵懂的女人 提交于 2020-01-31 02:02:57
前文主要介绍了@bean @ComponentScan 扫包注入两种方式，今天介绍一下@Conditional按照条件注入和@import导入组件的相关用法 1 首先是@Conditional的用法：按照一定的条件进行判断，满足条件给容器中注册bean，之前是写了@bean注解就会注入，但是在bean上加了@Conditional注解，并不一定就会注入了，而是进行条件判断之后再说， 该注解在springboot源码中大量用到，该注解是在spring4.0引入的。 首先我们创建一个Config，并且在里面注册2个person的Bean其中一个为windows另外一个为linux，使用@ Conditional注解来判断当前操作系统是windows还是linux分别加载不同的bean，见下图： package com.study.chap4.conditional.config; import com.study.chap4.conditional.Person; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Conditional; import org.springframework.context.annotation

data.table conditional Inequality join

由 谁说我不能喝 提交于 2020-01-30 06:00:26
问题 There're two sample datasets: > aDT col1 col2 ExtractDate 1: 1 A 2017-01-01 2: 1 A 2016-01-01 3: 2 B 2015-01-01 4: 2 B 2014-01-01 > bDT col1 col2 date_pol Value 1: 1 A 2017-05-20 1 2: 1 A 2016-05-20 2 3: 1 A 2015-05-20 3 4: 2 B 2014-05-20 4 And I need: > cDT col1 col2 ExtractDate date_pol Value 1: 1 A 2017-01-01 2016-05-20 2 2: 1 A 2016-01-01 2015-05-20 3 3: 2 B 2015-01-01 2014-05-20 4 4: 2 B 2014-01-01 NA NA Basically, aDT left join bDT based on col1, col2 and ExtractDate >= date_pol, only

.equals() or == when comparing the class of an object

由 六月ゝ 毕业季﹏ 提交于 2020-01-30 05:40:41
问题 In java, when you are testing what the object's class is equal to would you use .equals() or == For example in the code below would it be: if(object.getClass() == MyClass.class) or if(object.getClass().equals(MyClass.class)) 回答1: You can use instanceof for that kind of comparision too, anyway, The Class implementation don´t override equals so comparing using == is correct, it will check the runtime class, f.e: this code will shows true: public static void main(String[] args) { Object object =
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