本文介绍了TeX方程的Lexer规则(regex)的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

在TeX中,方程式在$...$之间定义.我如何为lex定义词法分析器规则,例如两个美元符号之间的任意数量的任何字符?

In TeX, equations are defined in between $...$. How can I define the lexer rule for lex, for the instance of any number of any characters between two dollar signs?

我尝试过:

equation  \$[^\$]*\$

没有成功.

推荐答案

您可以尝试使用开始条件,如果您不希望将美元符号包括在等式中:

You can try using start conditions if you don't want the dollar signs to be included as part of the equation:

%x EQN
%%
\$ { BEGIN(EQN); } /* switch to EQN start condition upon seeing $ */
<EQN>{
    \$ { BEGIN(INITIAL); } /* return to initial state upon seeing another $ */
    [^\$]* { printf(yytext); } /* match everything that isn't a $ */
}

如果在词法分析器中定义了其他状态,则可以使用yy_push_state()yy_pop_state()代替使用BEGIN(STATE).

Alternately instead of using BEGIN(STATE) you can use yy_push_state() and yy_pop_state() if you have other states defined in your lexer.

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07-28 03:36
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