“类型安全”是什么意思?
当前回答
类型安全的代码只访问它被授权访问的内存位置,并且只能以定义良好的、允许的方式访问。 类型安全代码不能在对象上执行对该对象无效的操作。c#和VB。NET语言编译器总是生成类型安全的代码,这些代码在JIT编译期间被验证为类型安全的。
其他回答
类型安全
在现代c++中,类型安全是非常重要的。类型安全意味着正确使用类型,因此避免不安全的类型强制转换和合并。c++中的每个对象都是根据其类型使用的,并且在使用之前需要对对象进行初始化。
安全初始化:{}
编译器在类型转换过程中防止信息丢失。例如, int {7};初始化没问题 \ . int b{7.5}编译器显示错误,因为信息丢失
不安全的初始化:=或()
编译器不会在类型转换期间防止信息丢失。 int a = 7初始化正常 int a = 7.5初始化正常,但信息丢失。a的实际值将变为7.0 int c(7)初始化OK int c(7.5)初始化是可以的,但是会发生信息丢失。a的实际值将变为7.0
来自文科专业而不是计算机科学专业的解释:
当人们说一种语言或语言特性是类型安全的时,他们的意思是该语言将有助于防止,例如,将非整数的东西传递给某个期望整数的逻辑。
例如,在c#中,我将一个函数定义为:
void foo(int arg)
编译器会阻止我这样做:
// call foo
foo("hello world")
在其他语言中,编译器不会阻止我(或者没有编译器…),所以字符串将被传递给逻辑,然后可能会发生一些不好的事情。
类型安全语言试图在“编译时”捕获更多。
缺点是,使用类型安全语言,当你有一个像“123”这样的字符串,你想像整型一样对它进行操作时,你必须写更多的代码来将字符串转换为整型,或者当你有一个像123这样的整型,并且想在一个像“答案是123”这样的消息中使用它时,你必须写更多的代码来将它转换/强制转换为字符串。
类型安全的代码只访问它被授权访问的内存位置,并且只能以定义良好的、允许的方式访问。 类型安全代码不能在对象上执行对该对象无效的操作。c#和VB。NET语言编译器总是生成类型安全的代码,这些代码在JIT编译期间被验证为类型安全的。
“类型安全”的编程语言意味着以下几点:
不能从未初始化的变量中读取 数组的索引不能超出它们的边界 不能执行未检查的类型强制转换
类型安全意味着可以分配给程序变量的值集必须符合定义良好且可测试的标准。类型安全变量导致程序更加健壮,因为操作变量的算法可以相信变量只接受定义良好的一组值中的一个。保持这种信任可以确保数据和程序的完整性和质量。
For many variables, the set of values that may be assigned to a variable is defined at the time the program is written. For example, a variable called "colour" may be allowed to take on the values "red", "green", or "blue" and never any other values. For other variables those criteria may change at run-time. For example, a variable called "colour" may only be allowed to take on values in the "name" column of a "Colours" table in a relational database, where "red, "green", and "blue", are three values for "name" in the "Colours" table, but some other part of the computer program may be able to add to that list while the program is running, and the variable can take on the new values after they are added to the Colours table.
Many type-safe languages give the illusion of "type-safety" by insisting on strictly defining types for variables and only allowing a variable to be assigned values of the same "type". There are a couple of problems with this approach. For example, a program may have a variable "yearOfBirth" which is the year a person was born, and it is tempting to type-cast it as a short integer. However, it is not a short integer. This year, it is a number that is less than 2009 and greater than -10000. However, this set grows by 1 every year as the program runs. Making this a "short int" is not adequate. What is needed to make this variable type-safe is a run-time validation function that ensures that the number is always greater than -10000 and less than the next calendar year. There is no compiler that can enforce such criteria because these criteria are always unique characteristics of the problem domain.
Languages that use dynamic typing (or duck-typing, or manifest typing) such as Perl, Python, Ruby, SQLite, and Lua don't have the notion of typed variables. This forces the programmer to write a run-time validation routine for every variable to ensure that it is correct, or endure the consequences of unexplained run-time exceptions. In my experience, programmers in statically typed languages such as C, C++, Java, and C# are often lulled into thinking that statically defined types is all they need to do to get the benefits of type-safety. This is simply not true for many useful computer programs, and it is hard to predict if it is true for any particular computer program.
长和短....您需要类型安全吗?如果是,那么编写运行时函数来确保当变量被赋值时,它符合定义良好的标准。缺点是它使域分析对于大多数计算机程序来说非常困难,因为您必须显式地为每个程序变量定义标准。