身份表达，因素和术语？ [英] Identity expression, factor, and term?

问题描述

我正在学习与上下文无关的语法，而且我不了解如何用C或C ++这样的编程语言来标识表达，因子和术语。

I am learning context-free grammar, and I don't understand how to identity expression, factor and term in a programming language like C or C++.

假设我们有一个赋值语句 id：= E ，其中E是任何算术表达式。

Suppose we have an assignment statement, id := E, where E is any arithmetic expression.

术语是什么？什么是表情？而实际代码中的因素是什么？

What is a term? What is an expression? and What is a factor in an actual piece of code?

我们可以拥有

int i = 3, j = 14
int i = 3 + j * 14;

非常感谢。

推荐答案

因数，项和表达式概念来自数学，与编程语言并没有真正的联系。

The "factor", "term" and "expression" concepts come from math and don't really have to do with programming languages.

因素就是您要乘的东西：

Factors are things you multiply:

1*2*(3+4)

添加的术语是：

1 + 2 + (3*4)

表达式是整个结果

1 + 3 * 7

在无上下文的语言解析中，您可以使用这些区别来组织运算符之间的优先级。因此，表达式由项的总和组成，而项由因子的乘积组成，并且因子可以是数字或带括号的子表达式。

In context-free language parsing you use these distinctions to organize the precedences between operators. So an expression is made of a sum of terms and a term is made of a product of factors and a factor is either a number or a parenthesized subexpression.

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