reclx中的tcl list index [英] tcl list index in regexp

问题描述

有没有办法在正则表达式中使用列表索引？

Is there a way to use the list index in a regexp ?

我已尝试过这个但它不起作用：

I've tried with this but it doesn't work :

if {[regexp {.*\[lindex $mylist 2\].*} $mystring]} {
    puts "OK"
} 

位于名单mylist列表的索引2处的值未被替换在正则表达式。

the value located at list index 2 of the list named mylist is not replaced in the regexp.

谢谢。

推荐答案

如果你只是想要要查看另一个简短字符串是否存在， regexp 是不正确的方法。相反，首先使用字符串：

If you just want to see if some short simple string is present in another, regexp is not the right approach. Instead, use string first:

if {[string first [lindex $mylist 2] $mystring] >= 0} {
    puts "OK"
}

如果列表的第三个元素中确实有正则表达式，那么这就足够了，因为Tcl总是检测到RE是否匹配任何地方（默认情况下它的模式是非锚定的）：

If the list really has a regular expression in its third element, then it's enough to do this because Tcl always detects if an RE matches anywhere (it's patterns are unanchored by default):

if {[regexp -- [lindex $mylist 2] $mystring]} {
    puts "OK"
}

- 以防止RE以 - 字符，可能会导致混淆。您还可以使用 regexp 来使用类似字符串的第一个食谱：

The -- is just in case the RE starts with a - character, which can cause confusion. You could also use regexp to work a bit like that string first recipe:

if {[regexp ***=[lindex $mylist 2] $mystring]} {

但是字符串优先的代码会更快！如果你想要比这更复杂的东西，那么停止并思考你所做的是否是正确的方法可能是一个好主意;当一个人发现自己在正则表达式中进行复杂的替换时，通常会陷入混乱。 （或者至少当我知道我需要重新考虑时。）在这里询问 - 同时提供更多的背景 - 可以帮助你解决问题。

But the code with string first will be faster! If you want anything much more complicated than this, it's probably a good idea to stop and think whether what you're doing is the right approach; when one finds oneself doing complicated substitutions in regular expressions, one is usually getting into a mess. (Or at least that's when I know I need to rethink.) Asking here — while providing a bit more context — can help you figure things out.

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