精华内容
下载资源
问答
  • whatis命令

    2016-06-13 11:47:00
    whatis——于查询一个命令执行什么功能 示例1: # whatis ls 显示ls命令的功能,和执行man命令时NAME信息差不多 转载于:https://www.cnblogs.com/zuhua/p/linux-whatis.html...

    whatis——于查询一个命令执行什么功能

     

    示例1:

    # whatis ls 

    显示ls命令的功能,和执行man命令时NAME信息差不多

     

    转载于:https://www.cnblogs.com/zuhua/p/linux-whatis.html

    展开全文
  • It looks like you're trying to connect to your database from a different ... Is your PHP script still running on your own PC?The message you get is because you try to reach the database from the c...

    It looks like you're trying to connect to your database from a different server. Is your PHP script still running on your own PC?

    The message you get is because you try to reach the database from the computer at address 31.170.163.50, which is not allowed. Quite often, when you have 'normal' simple, shared hosting, you are not allowed to use the database from other computers directly. Only the scripts on the server itself are allowed to use the database.

    So, the solution would be: Put everything, scripts and database, on your web hosting platform, and use localhost or 127.0.0.1 when your PHP script needs to connect to your database.

    展开全文
  • 如题:what is method signature in java? answer:Definition: Two of the components of a method declaration comprise the method signature—the method's name and the parameter types. 方法声明的两个组件...

    如题:what is method signature in java? 

    answer:Definition: Two of the components of a method declaration comprise the method signature—the method's name and the parameter types.

    方法声明的两个组件构成了方法签名 - 方法的名称和参数类型。

    举例:

    Here is an example of a typical method declaration:(这里是一个典型的方法声明)

    public double calculateAnswer(double wingSpan, int numberOfEngines,
                                  double length, double grossTons) {
        //do the calculation here
    }

    The signature of the method declared above is:(上面方法的签名是)

    calculateAnswer(double, int, double, double)

     

    不要再被方法签名迷惑了,之前读Effective Java的时候对这个概念有些疑惑。正好在看oracle的java 练习文档中有明确的定义。

    展开全文
  • What is a Parse Tree? Author's name: Carel-Jan Engel Author's Email: cjpengel.dbalert@xs4all.nl ...

    What is a Parse Tree?


    Author's name: Carel-Jan Engel

    Author's Email: cjpengel.dbalert@xs4all.nl

    Date written: Mar 24, 2005

    Oracle version(s): N/A

    In documentation about tuning SQL, I see references to parse trees. What is a parse tree ?

    Back to index of questions


    A parse-tree is an internal structure, created by the compiler or interpreter while parsing some language construction. Parsing is also known as 'syntax analysis'.

    An example (slightly adapted version of the example found at page 6 of the famous 'Dragon Book', Compilers: principles, techniques and tools, by Alfred V. Aho, Ravi Sethi and Jeffrey D. Ullman, Published by Addison Wesley. My copy is from 1986) will illustrate a parse tree. Rather than dealing with the complexities of a SQL statement, let's take a rather simple language construction: The assignment of the result of an expression to a variable:

    result := salary + bonus * 1.10

    When the compiler analyzes this statement the resulting parse-tree will look like this :

                       assignment

               ________ statement ____

              /             |         \

             /             :=          \

        identifier              ___ expression _______

            |                  /         |            \

          result              /          +             \

                         expression              __ expression ___

                             |                  /       |         \

                         identifier            /        *          \

                             |            expression            expression

                           salary             |                     |

                                          identifier              number

                                              |                     |

                                            bonus                  1.10

    The picture is an upside-down representation of a tree. The language elements in this small simple assignment are: identifiers (result, salary, bonus), operators (:=, +, *), and a number (1.10). 'Identifier' is the language element that names a variable, function or procedure. 'Operator' is the language element that represents some action to be taken, upon the operands at either end of the operator. Number is a constant, 1.10 in this statement. The syntax rules (' grammar') will specify which 'sentences' are valid.

    After successfully decomposing the statement into its internal representation, the compiler or interpreter can 'walk the tree' to create the executable code for the construction. An interpreter will not generate code for the execution, but will invoke built-in executing functions by itself. Let's take the interpreter for the rest of the explanation, execution of the steps is easier to explain than the code-generation of a compiler. For the example I assume the bonus to be 100, and the salary to be 1000. The tree-walk will start at the root of the tree, the assignment statement. The rule for the assignment will tell the interpreter that the right hand has to be evaluated first. This evaluation is also known as 'reduction'. The right hand side of the assignment needs to be reduced to a value, the result of the expression, before it can be assigned to the variable at the left hand side of the statement.

    The first node at the right-hand side of the statement contains an expression with a '+' operator. The right hand side of the '+' operator needs to be assigned to the left hand side. So the walk goes on to the next node at the right hand side. There the interpreter will detect the expression with the '*' operator. The left hand side of this operator needs to be multiplied with the right hand side. The interpreter goes on to the right hand side, and detects an expression that consists of a single number: 1.10. This side is fully reduced, the result can be stored and the interpreter walks the tree back up to the '*' operator, and starts evaluating its left hand side. This is an expression that consists of one single identifier, representing a variable, 'bonus'., The memory location represented by this variable is read and it's contents (100) will be multiplied by the right hand side result, 1.10. This expression has been fully reduced to the result 110 now. The interpreter walks up, to the '+' operator, and starts evaluating its left hand side. There it will again detect an identifier, 'salary'. Its location is read (1000) and the expression is reduced to a number, 1000. The right and left hand side will be added, resulting in 1,110. Now the expression at the right hand side of the assignment is fully reduced, and the interpreter walks up the tree, finds the assignment operator ':='. This instructs the interpreter to copy the result of the expression to the left hand side. The left hand side contains an identifier, 'result'. The memory location represented by 'result' will be filled with the result of the expression, 1,110.

    It is just a simplified explanation of how an interpreter or compiler uses a parse tree. It's out of scope of this answer to create a complete introduction to compiler building practices. However, it might be clear that creating a parse-tree consumes some resources. Before the language elements can be recognized they must be read character by character, type checking and possible conversion needs to be done, identifiers (tables, columns etc.) need to be identified and checked in the data dictionary, and so on. After this 'hard parse' the parse tree is composed, and is a far cheaper form. to use to execute a statement than doing all this analysis over and over again. Therefore, storing the parse-tree in the SQL-area for future use can save quite some time during the processing of SQL-statements that have come across before.

     

    http://www.jlcomp.demon.co.uk/faq/parse-tree.html  

    来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/35489/viewspace-676754/,如需转载,请注明出处,否则将追究法律责任。

    转载于:http://blog.itpub.net/35489/viewspace-676754/

    展开全文
  • Whatis DNS

    2017-06-30 20:33:56
    什么是DNS 域名 如:www.baidu.com,这是一个主机名, 它实际上有一个明确的定义叫Full Qualified Domain Name,即完全限定域名.这个主机名对应的真正域名是.com和.baidu.com.由此可知,其实域名,是指一定范围内主机名的...
  • 什么是解析树?What is a Parse Tree?

    万次阅读 2011-08-31 17:06:29
    The Oracle (tm) Users' Co-Operative FAQ What is a Parse Tree? Author's name: Carel-Jan Engel Author's Email: cjpengel.dba
  • What is DUAL table in Oracle

    2015-01-03 23:38:19
    起源 使用oracle的时候,我们经常会运行下面的sql得到当前系统时间: sqlSQL> select sysdate from dual;...我想看看dual是什么,运行一下desc sqlSQL> desc dual; Name Null? Type -------
  • what is the oracle cursor?

    2008-12-31 10:09:00
    什么是CURSOR,ORACLE的文档作了如下定义:A cursor is a handle (a name or pointer) for the memory associated with a specific statement. (Oracle Call Interface, OCI, refers to these as statement handles....
  • 今天就来看一些什么是uri url urn。看看uri:A URI can be further classified as a locator, a name, or both. The term "Uniform Resource Locator" (URL) refers to the subset of URIs that, in additio
  • Bundle display name - is what will be shown on iPhone screen,即当你安装该app到iPhone上显示的name。 注意:Bundle Display name must correspond to Bundle name,即bundle display name和bundle name不能...
  • ... ... <pre><code><...input type="checkbox" id="1">...<p>What should I use instead of this? <pre><code>if(!isset($_POST['2'])) </code></pre> <p>I can't use jQuery due to professor limitations. </div>
  • man 功能:查看命令或文件配置的帮助信息 语法:man [命令或配置文件名] 示例:查看ls命令的帮助信息,主要查看NAME,可以理解其是做什么的;man ls 复制代码 示例:查看services配置文件的帮助说明,man后面直接加...
  • Office Delve 初窥 - What is Office Delve?

    千次阅读 2015-10-13 16:00:50
    Office Delve (codename Oslo) 是由微软于2014年7月发布的Office 365的最新成员,它为Office 365用户提供了方便的搜索和邮件、会议、联系人、社交网络等管理功能,并通过用户的行为以及与内容、主题和联系人的关系...
  • 比如生活中我们同事遇到时经常会相互问对方在做什么项目哇,一般基本都会回答说自己在某某[name]项目上,本篇就简单来捋一捋项目周边。 项目,在一定时间和资源条件下为达到某个目标而进行的相关活动,简单来说即...
  • <p>Can someone explain to me word by word, what is meant by $this->name=$name? I keep thinking like, $this goes into(hence the -> sign) name which is (hence the = sign) $name defined beforehand....
  • A simple makefile consists of “rules” with the following shape(一个简单的makefile由一系列的规则构成,规则样式如下): target(目标) … : prerequisites(依赖) … ...A target is usually the name...
  • <p>What is going on? Why don't I have this folder? <p>EDIT: I downloaded it from here <a href="https://golang.org/dl/" rel="nofollow noreferrer">https://golang.org/dl/</a> for mac</p> </div>
  • <p>I tried some googling and get to know that here <strong>businesses</strong> is pod name and <strong>address_city</strong> and <strong>business_approved</strong> are the column names for the pod. ...
  • <p>what is contents in parenthesis before MethodName? I mean this (t *T) <p>This comes from here: <a href="http://golang.org/pkg/net/rpc/" rel="nofollow">http://golang.org/pkg/net/rpc/</a> I try to ...
  • <p>what am I doing wrong? <p>I would like to return one value taken from doctrine. <p>Edit: When I changed the definition route_name = user_method, I have an error with the POST method: <p>...
  • <p>When would you consider using one over the other and why?...转载于:https://stackoverflow.com/questions/2297403/what-is-the-difference-between-http-host-and-server-name-in-php</p>
  • <p>So what I am doing is I ... Sorry for the long question wanted to be as descriptive as possible and show that in File1 what $GLOBALS['me'] is set and in File2 it is empty or null. Thanks! </div>
  • <p>So what would be the cause of these blanks? I also tried $_GET</code> doesn't help much. <p><strong>*****[EDIT]*********</strong></p> <pre><code><form id="vote-form" action="/some/path?r=shop...
  • 文章转发自专业的Laravel开发者社区,原始链接:https://learnku.com/laravel/t/15077/what-is-the-n1-problem-and-how-to-solve-the-n1-problem-in-laravel对象关系映射(ORM)使得处理数据惊人地简单。由于以面向...
  • <p>When i write - <code>if(isset($_POST['...<p><strong>The output i get is "default" and not what i type in input field in the html</strong> form.. Can you tell why? Thanks in advance.</p> </div>
  • <p>So, what we do is this: We take $mailData, and we convert each key name to the uppercase version. So if they submit "toAddReSs", it will be evaluated as "TOADDRESS",in all uppercase lettering - to ...

空空如也

空空如也

1 2 3 4 5 ... 20
收藏数 1,009
精华内容 403
关键字:

iswhat什么name