英文:
string.find fails with a hyphen
问题
我用Lua开始制作Factorio模组，出现了一个有趣的问题：我无法正确执行Lua中的简单子字符串搜索。string.find可以正确找到"-mining-"或"-drones"，但不能同时找到带有连字符的两个单词。如何修复这个问题？
local str = "copper-ore-mining-drone-10"
local sub = "mining-drone"
print(str:find(sub))
快速测试链接：
https://www.lua.org/cgi-bin/demo
也许find使用了某种模式语法，连字符并非字面意义上的字符？但我在文档中找不到相关信息，并且尝试转义它-"会导致"无效的转义序列"错误。如果需要进行某种转义，我如何可以自动完成？因为我从外部来源接收子字符串值。
英文:
I started making Factorio mods with Lua, and a funny problem appeared: I cannot correctly perform a simple substring search in Lua. string.find can correctly find "-mining-" or "-drones", but not both words with a hyphen. How to fix this??
local str = "copper-ore-mining-drone-10"
local sub = "mining-drone"
print(str:find(sub))
For quick testing:
https://www.lua.org/cgi-bin/demo
Maybe find uses some pattern syntax and a hyphen isn't used literally? But I found nothing about it in the docs, and trying to escape it -" leads to invalid escape sequence error. In case it requires some escaping, how can I do this automatically? Cuz I receive substring value from an external source.
答案1
得分: 2
经过更多搜索，我发现find方法实际上使用了一些表达式语法（奇怪的是文档中没有解释）。有一些解决方法：
1. 使用转义符号%
看起来Lua的搜索表达式语法使用%作为转义字符：
str:find("mining%-drone")
2. 设置plain标志
该方法有一些参数，这些参数也没有在文档中提到，第三个参数是plain标志，它允许将子字符串视为字面值：
str:find(sub, 1, true)
英文:
After more googling, I found that yeah, find method really uses some expression syntax (strange that it's not explain in the docs). There is a couple of solutions:
1. Use escape symbol %
Seems like lua's search expression syntax uses % as an escape character:
str:find("mining%-drone")
2. Set plain flag
The method has some arguments that also aren't mention in the docs, the third one is plain flag which allows to treat a substring literally:
str:find(sub, 1, true)
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