list 如何检查TCL中是否存在列表元素？
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How to check if list element exists in TCL?
提问by Narek
Say I have a TCL list, and I have append some elements to my list. Now I want to check if I have appended 6 or 7 elements.
假设我有一个 TCL 列表，并且我已将一些元素附加到我的列表中。现在我想检查我是否附加了 6 或 7 个元素。
In order to check if list element exists in the place specified by an index I have used:
为了检查列表元素是否存在于我使用的索引指定的位置：
if { [info exists [lindex $myList 6]] } {
#if I am here then I have appended 7 elems, otherwise it should be at least 6
}
But seams this does not work. How I should do that? properly? It is OK to check if { [lindex $myList 6]] eq "" }
但是接缝这不起作用。我该怎么做？适当地？可以检查{ [lindex $myList 6]] eq "" }
回答by überjesus
Why don't you use llengthto check the length of your list:
你为什么不用llength来检查你的列表的长度：
if {[llength $myList] == 6} {
# do something
}
Of course, if you want to check the element at a specific index, then then use lindexto retrieve that element and check that. e.g. if {[lindex $myList 6] == "something"}
当然，如果您想检查特定索引处的元素，则使用lindex来检索该元素并进行检查。例如if {[lindex $myList 6] == "something"}
Your code using the info existsis not working, because the info existscommand checks if a variable exists. So you are basically checking if there is a variable whose name equals the value returned by [lindex $myList 6].
您使用 的代码info exists不起作用，因为该info exists命令会检查变量是否存在。因此，您基本上是在检查是否存在名称等于[lindex $myList 6].
回答by FriendFX
I found this question because I wanted to check if a list contains a specific item, rather than just checking the list's length.
我发现这个问题是因为我想检查列表是否包含特定项目，而不仅仅是检查列表的长度。
To see if an element exists within a list, use the lsearchfunction:
要查看列表中是否存在元素，请使用以下lsearch函数：
if {[lsearch -exact $myList 4] >= 0} {
puts "Found 4 in myList!"
}
The lsearchfunction returns the index of the first found element or -1if the given element wasn't found. Through the -exact, -glob(which is the default) or -regexpoptions, the type of pattern search can be specified.
该lsearch函数返回第一个找到的元素的索引，或者-1如果未找到给定的元素。通过-exact, -glob（这是默认值）或-regexp选项，可以指定模式搜索的类型。
回答by Andrew Rooney
Another way to check for existence in a list in TCL is to simply use 'in', for instance:
在 TCL 中检查列表中是否存在的另一种方法是简单地使用“in”，例如：
if {"4" in $myList} {
puts "Found 4 in my list"
}
It's slightly cleaner/more readable!
它更干净/更具可读性！
