When this macro executes, it will match the my-if expression up to the template like this (in other words, matching a macro invocation to a macro definition pattern).

在这个宏执行时，它按照以下形式将my - if表达式与模板进行匹配(换句话说，将宏调用与宏定义模式进行匹配)。

youdao

He began to walk about, looking up in the trees and at the walls and bushes with a thoughtful expression.

他开始四处走动，向上望着树木、墙壁和灌木丛，脸上带着若有所思的表情。

youdao

The main part of pattern matching is coming up with the expression to use.

模式匹配的主要部分是关于要使用什么样的表达式。

youdao

And that's one of the things Jacob was noted for. His level of expression is so profound that even with a few strokes, he can pick up the action and show it to you".

VOA: special.2009.09.02

When Israel dares to complain about these attacks, European politicians and media celebrities are quick to stand up and defend their right to freedom of expression.

CENTERFORSECURITYPOLICY: Mainstreaming anti-Semitism

The mandatory new rules required artists to give up any form of individual self-expression, since every creative impulse was to be filtered through the tight grip of Communist Party orthodoxy.

CNN: ASIANOW - TIME Asia | Visions of China: China Art Gallery

Koberna is accused of posting on the public account of social networking site Twitter a threat on Wednesday "laced with profanity, mentioned Kent State University by name (and) also mentioned our president by name and concluded with the expression that he was going to shoot up the campus, " said university spokesman Eric Mansfield.

MSN: Kent State student charged after Twitter threats - Technology & science - Security | NBC News