Re: [Boost-users] [date_time] extract date from string using a list of patterns

From: Jason Dolan (jason_at_[hidden])
Date: 2006-06-27 12:33:58

Jeff Garland wrote:
> Jason Dolan wrote:
>> Jeff Garland wrote:
>>> Jason Dolan wrote:
>>>> I'm looking to take a string and convert it to a date.  The only problem 
>>>> is the string can be one of many patterns. i.e. ("%Y%m%d", "%Y-%m-%d", 
>>>> "%d/%m/%Y", etc...).  It is also possible that the given string will 
>>>> fail all pattern matches, and thus return false.
>>> And there's nothing to indicate which pattern it might be?
>> Nope.  I'm basically allowing the user to input a date and time *almost* 
>> anyway they want.  What I want to do is test that string against my list 
>> of patterns(i.e. known ways to write a date and time) to try and parse 
>> the date.
> 
> Well, again some of them are going to be ambiguous.  And I'll just say, this 
> is a big (read not doable) undertaking.  Are all these valid?  They certainly 
> are to someone somewhere:
> 
>    june 5 2006
>    june 5, 2006
>    june 5, 06
>    jun 5        //just assume the current year
>    junio 5, 2006  //spanish
>    5-jun-2006
>    5-june-2006
>    05-June-2006
>    05    JUNE 2006
>    7/5/6
>    7/6/5
>    5/6/7
>    07/05/06
>    05-07-06
>    05.07.06
>    050706
Yikes! Maybe I'll be a little more restrictive... like force 4 digit 
years, etc...

...snip...

> 
> You could refactor your code so you don't reallocate the stringstream and 
> facet (just reset the strings and formats). But if you really need a high 
> level of efficiency, then you're going to just have to bite the bullet and 
> write a custom parser.  The iostreams solution will always be inherently less 
> efficient than custom solutions.
Thats why I was looking into it this way, I was hoping not to have to 
create my own parser.  I'm actually kinda of surprised that there isn't 
a open source natural language date string parser out there already.

> 
> Jeff