Searching for symbols is a common in programming, especially when you are new to a language.
For example, I had a question about the :: operator in Python, and that is not searchable. People looking for things like this or Object [] (array of Objects), would not find what they want.
Why do search engines seem to ignore symbols completely? They are just characters like any others. I can see why it would be hard to extract semantics from symbols compared to words (eg: a search engine can figure out that "find," "finds," "found" are all related, if not the same word), but is it really that hard to search for them?
I can also see why in everyday use you'd want symbols to be ignored, but how hard would it
be to make it look for something explicitly (eg: "::" would search for ::)
Check out this article on Interpreting Google Search Queries.
Specifically, section 9
Google ignores some punctuation and special characters, including ! ?, . ; [ ] @ / # < > .
Because punctuation is typically not as important as the text around it, Google ignores most punctuation in your search terms. There are exceptions, e.g., C++ and $99. Mathematical symbols, such as /, <, and >, are not ignored by Google's calculator.
[ Dr. Ruth ] returns the same results as [ Dr Ruth ]
What if you're seeking information that includes punctuation that Google ignores, e.g., an email address? Just enter the whole thing including the punctuation.
* [ info@amazon.com ]Be aware that web pages sometimes camouflage email addresses to make collecting such information difficult for spammers. For example, on some sites you'll find the @ sign in an email address replaced with the word “at.”
Now we'll look at some special characters that Google doesn't ignore.
To minimize the number of entries in the index.
A search engine doesn't have to ignore them though. For example, it seems Google Code doesn't.
来源：https://stackoverflow.com/questions/3737172/why-do-search-engines-ignore-symbols