Lua 中的字符串操作

Question

I have a string in which I have to replace some characters (or to delete, which is the same here). The important part is marked by the character @ . the charcters before it should be replaced by the following ones, independet on the number of characters before and behing the @ . The end of the string on the right side of @ is given by line end or the characters ! and | . Some examples

str0 = "whatever"                 -- do nothing
str1 = "whatever!whenever!time"   -- do nothing
--
-- the following should replace only "little" by "big"
-- means "little@big"  -> "big"
--
str2 = "little@big"  
str3 = "Size!little@big"
str4 = "Whatever!Size!little@big!whatever"
str5 = "Whatever!little@big!whatever!little@big"
str5 = "Whatever!little@big!whatever!little@big!little@big"
str6 = "Whatever!little@big!whatever!little@big!little@big|foo"

the numbers of @ is not known. Is there an "easy" code to modify the string?

Answer 1

str = str:gsub('[^!|@%s]+@', '')