parameter和argument的差別

轉載自： http://smilejay.com/2011/11/parameter_argument/

在對一個函數寫一個注釋時，我在考慮到底該用parameter還是用argument來描述其參數呢。

根據網上一些資料，對parameter和argument的差別，做如下的簡單說明。

1. parameter是指函數定義中參數，而argument指的是函數調用時的實際參數。

2. 簡略描述為：parameter=形參(formal parameter)， argument=實參(actual parameter)。

3. 在不很嚴格的情況下，現在二者可以混用，一般用argument，而parameter則比較少用。

While defining method, variables passed in the method are called parameters.

當定義方法時，傳遞到方法中的變量稱為參數.

While using those methods, values passed to those variables are called arguments.

當調用方法時，傳給變量的值稱為引數.（有時argument被翻譯為“引數“）

一個C++的例子來說明二者的差別：

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void func(int n, char * pc); //n and pc are parameters template <class T> A {}; //T is a a parameter   int main() { char c; char *p = &c; func(5, p); //5 and p are arguments A<long> a; //'long' is an argument A<char> another_a; //'char' is an argument return 0; }

如下叙述，來自wikipedia:

http://en.wikipedia.org/wiki/Parameter_%28computer_programming%29

Just as in standard mathematical usage, the argument is thus the actual value passed to a function, procedure, or routine (such as x in log x), whereas the parameter is a reference to that value inside the implementation of the function (log in this case). See the Parameters and arguments section for more information.

Parameters and arguments

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These two terms are sometimes loosely used interchangeably; in particular, “argument” is sometimes used in place of “parameter”. Nevertheless, there is a difference. Properly, parameters appear in procedure definitions; arguments appear in procedure calls.

A parameter is an intrinsic property of the procedure, included in its definition. For example, in many languages, a minimal procedure to add two supplied integers together and calculate the sum total would need two parameters, one for each expected integer. In general, a procedure may be defined with any number of parameters, or no parameters at all. If a procedure has parameters, the part of its definition that specifies the parameters is called its parameter list.

By contrast, the arguments are the values actually supplied to the procedure when it is called. Unlike the parameters, which form an unchanging part of the procedure’s definition, the arguments can, and often do, vary from call to call. Each time a procedure is called, the part of the procedure call that specifies the arguments is called the argument list.

Although parameters are also commonly referred to as arguments, arguments are more properly thought of as the actual values or references assigned to the parameter variables when the subroutine is called at run-time. When discussing code that is calling into a subroutine, any values or references passed into the subroutine are the arguments, and the place in the code where these values or references are given is the parameter list. When discussing the code inside the subroutine definition, the variables in the subroutine’s parameter list are the parameters, while the values of the parameters at runtime are the arguments.

Many programmers use parameter and argument interchangeably, depending on context to distinguish the meaning. The term formal parameter refers to the variable as found in the function definition (parameter), while actual parameter refers to the actual value passed (argument).