Can I redirect "cin" to function with regex?

Question

I'm having my head around for a couple of days with this question, and I still can't solve my problem.

If I need to read two strings from keyboard I can do this:

cin >> str1 >> str2;

However I want to filter the input.

What I'm trying to do, is something like this:

cin >> filter1 >> str1 >> filter2 >> str2;

or alternatively

cin >> filter1 >> filter2 >> str1 >> str2;

Where filter1 and filter2 are functions with regexes for filter the input.

My biggest trouble is I can't see how to insert the functions, between the input and the strings. .

Any help appreciated

Would you tolerate `>> filter(str1)`? I think that would be easier to implement. — Bathsheba, Nov 25 '16 at 11:21
Yes, but in that case would be cin >> filter1(str1) >> filter2(str2)? Like that? — user7140484, Nov 25 '16 at 11:22
Sorry my last comment was hogwash. I thought you could get away with `filter(str1) >> filter(str2)` — Bathsheba, Nov 25 '16 at 11:24
You can easily create you own *manipulators* similar to the standard manipulators. However the problem here, I think, is the actual *filtering*. I don't think there is a way to skip the next extraction. So a solution where you create a manipulator that takes the variable as an argument (as suggested by @Bathsheba) would be the best solution. — Some programmer dude, Nov 25 '16 at 11:28
`filter` would actually be a class which has a constructor to a string type. It then has an overloaded >> to an istream. — Bathsheba, Nov 25 '16 at 11:28
Please [find a good book to read](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). That will teach you how to overload operators like `>>`. — Some programmer dude, Nov 25 '16 at 11:36
@Someprogrammerdude, I know how to do operator overloading. The problem is the iostream. — user7140484, Nov 25 '16 at 11:37
Overloading the input and output (actually the bitwise shift operators) for streams is no different than overloading other functions and operators. Again, please pick up a book as it will tell you everything you need to know. — Some programmer dude, Nov 25 '16 at 11:40
@Someprogrammerdude, I follow your advice and already know how to overload `>>` and `<<` with `istream` and `ostream`. My problem is solved. — user7140484, Nov 25 '16 at 17:04

score 0 · Answer 1 · answered Nov 25 '16 at 12:19

Your filter function should return object of class that implements filtering using regex. Then you would overload operator>> to accept that object, which would read data and invoke it. Peek into istream header to get idea how to do that. Object must be destroyed or it may be a singleton of some kind

Can I redirect "cin" to function with regex?

1 Answers1