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【導(dǎo)讀】大連交通大學(xué)2021屆本科生畢業(yè)設(shè)計(論文)外文翻譯

  

【正文】 seem. If there’s a downside, it is the expense of the learning curve. Thinking in objects is a dramatic departure from thinking procedurally, and the process of designing objects is much more challenging than procedural design, especially if you’re trying to create reusable objects. In the past, a novice practitioner of objectoriented programming was faced with a choice between two daunting tasks: 1. Choose a language such as Smalltalk in which you had to learn a large library before being productive. 2. Choose C++ with virtually no libraries at all,1 and struggle through the depths of the language in order to write your own libraries of objects. 面向?qū)ο蟪绦蛟O(shè)計吸引著多個層面。對于經(jīng)理人( managers),它提供了更快速、更廉價的開發(fā)和維護(hù)( maintenance)費用。對于分析員和設(shè)計人員,建模過程( the modeling process)變得更簡單而且可以創(chuàng)建一個有序而可控的設(shè)計。對于程序員而言,簡潔而優(yōu)雅的對象,強有力的面向?qū)ο蠊ぞ吆烷_發(fā)庫將為他們創(chuàng)造一個愉快的開發(fā)環(huán)境,并且體驗到生產(chǎn)效率的提高。它將會使每個人都受益。 如果說有不好的一面,那就是昂貴的學(xué)習(xí)曲線( learning curve)。用對象的方式來思考問題相比于過程化的思考問題 方式有著很大的差別,而且設(shè)計一個對象比起設(shè)計一個過程來說是一個很大的挑戰(zhàn),特別是當(dāng)你要設(shè)計一個可復(fù)用的對象( reusable objects)的時候。在過去,一個從事面向?qū)ο蟪绦蛟O(shè)計的初級從業(yè)人員面對著兩大難題: 選擇一個像是 Smalltalk 一樣的語言,如果你想要用它來進(jìn)行生產(chǎn)你就必須要學(xué)習(xí)一個很大型的庫。 選擇一個像是 C++語言一樣的語言,幾乎沒有任何的庫。你必須去設(shè)法了解深澀的語言本身以便于去編寫你自己的對象庫。 1 Fortunately, this has change significantly with the advent of thirdparty libraries and Standard C++ library. 頁 40 It is, in fact, difficult to design objects wellfor that matter, it’s hard to design anything well. But the intent is that a relatively few experts design the best objects for others to OOP languages incorporate not just language syntax and a piler, but an entire development environment including a significant library of welldesigned , easy to use ,the primary job of most programmers is to use existing objects to solve their application problems. The goal of this chapter is to show you what objectoriented programming is and how simple it can be. 事實上,把設(shè)計對象好是一件很難的事情。而且,設(shè)計每個東西其實都是很難的。這就是它的目的所在,讓相對很少的一部分專家去設(shè)計最好的對象,讓其余的人去使用它們。幸運的是,面向?qū)ο蟪绦蛟O(shè)計語言并不只是有其語法和一個編譯器,而是有一個完整的開發(fā)環(huán)境包含一個被設(shè)計良好并且專業(yè)的庫,使調(diào)用對象變得很簡單。因此,對于大多數(shù)程序員來說主要的工作是使用這些現(xiàn)成的對象去處理他們的程大連交通大學(xué) 2021 屆本科生畢業(yè)設(shè)計(論文)外文翻譯 12 序所要解決的問題。本章的木的正是要告訴你什么是面向?qū)ο蟪绦蛟O(shè)計,然后如何簡化它。 The Chapter will introduce many of ideas of Java and Objectoriented programming on a conceptual level, but keep in mind that you’re not expected to be able to write fullfledged Java Programs after reading this chapter. All the detailed descriptions and examples will follow throughout the course of this book. 這一章將會在概念層面上引導(dǎo)你去接觸很多 Java 和面向?qū)ο蟪绦蛟O(shè)計思想,但是不要指望通過閱讀這一章就寫出一個完整的 java 程序。所以地細(xì)節(jié)描述和例子將會貫穿整本書。 The progress of abstraction 抽象進(jìn)階 All programming languages provide abstractions. It can be argued that the plexity of the problems you can solve is directly related to the kind and quality of abstraction. By “kind” I mean : what is it that you are abstracting? Assembly language is a small abstraction of the underlying machine. Many socalled “imperative” languages that followed(such as FORTRAN, BASIC, and C)were abstractions of assembly language. These languages are big improvements over assembly language, but their primary abstraction still requires you to think in terms of structure of the puter rather than the structure of the problem you are trying to solve. The programmer must establish the association between the machine model(in the “solution space”) and the model of the problem that is actually being solved (in the “problem space”). The effort required to perform this mapping, and the fact that it is extrinsic to the programming language, produces programs that are difficult to write and expensive to maintain, and as a side effect created the entire “programming methods” industry. 所有的程序設(shè)計語言都提供了抽象。通常你能處理的問題的復(fù)雜度的爭議是直接與抽象的類型和質(zhì)量有關(guān)。我之于 “kind”的定義是:那些你正在抽象的東西,比如說:匯編語言是一種針對于底層機器的小型抽象。很多被稱作命令式( “imperative”)語言,如( FORTRAN, BASIC, 或 C)是基于匯編語言之上的抽象。這些語言是在匯編語言之上的一個大的提升,但是它們的主要抽象依據(jù)仍然是匯編語言,我們?nèi)匀灰诳紤]如何用程序解決問題的同時考慮程序在計算機結(jié)構(gòu)上的實現(xiàn)。程序員必須建立一個在機器模型(解空間)和問題模型(問題空 間)之間的關(guān)聯(lián)。這種努力需要創(chuàng)建一個關(guān)聯(lián)圖,這其實是程序設(shè)計語言本身之外的東西,創(chuàng)建程序變得難于書寫而且需要花費昂貴的代價用于維護(hù),這對于整個程序設(shè)計方法工業(yè)是一個副作用。 The alternative to modeling the machine is to model the problem you’re trying to solve. Early languages such as LISP and APL chose particular views of the world (“all problems are ultimately lists” or “all problems are algorithmic”). PROLOG casts all problems into chains of decisions. Languages have been created for constrainbased programming and for programming exclusively by manipulating graphical symbols. (The latter proved to be too restrictive.) Each of these approaches is a good solution to the particular class of problem they’re designed to solve, but when you step outside of that domain they bee awkward. 我們應(yīng)該把對機器建模替換為對對我們所要處理的問題進(jìn)行建模。早期的語言如 LISP 和 APL 選擇特殊的對世界的視角( “所有的問題都是無限序列 ”或者 “所有的問題都可以用算法來表達(dá) ”)。 PROLOG把所有的問題都?xì)w類為決策鏈。語言被創(chuàng)造為基于約束的編程并且有專門用來操作圖形對象的編程。(后來增加了更多的限制)。以上這些每一種都是為了達(dá)到一個處理特殊種類問題的目的而創(chuàng)建,一旦你的問題在其處理范圍之外,它們將不再有用武之地。 The objectoriented approach takes a step farther by providing tools for the programmer to represent elements in the problem space. This representation is general enough that the programmer is not 大連交通大學(xué) 2021 屆本科生畢業(yè)設(shè)計(論文)外文翻譯 13 constrained to any particular type of problem. We refer to the elements in the problem space and their representations in the solution space as “objects.” (Of course, you will also need other objects that don’t have problemspace analogs.) The idea is that the program is allowed to adapt itself to the lingo of the problem by adding new types of objects, so when you read the code describing the solution, you’re reading words that also express the problem. This is a more flexible and powerful language abstraction than what we’ve had before. Thus OOP allows you to describe the problem in terms of problem rather than in the terms of the solution. 面向?qū)ο蟮姆椒ǜM(jìn)了一步,通過向提供程序員一些用于表示元素的工具。這種程度的表示形式基本上足夠程序員不受約束的處理各種特殊類型的問題。我們引用那些問題空間中的元素和它們的表現(xiàn)形式作為對象(當(dāng)然,你仍然可以使用不在問題空間中有對應(yīng)元素的對象)。這種概念允許程序去適應(yīng)它自己方言通
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