From: "Ovanes Markarian"
Now I have an instance of struct C and would like to know if x is a valid pointer. this code is really ugly:
if(c.b_) if(c.b_.a_) if(c.b_.a_.x) //do smth ...
The intention would be to write everything in one if-statement. It is not possible to implement a bool or ! operator in these structures, since these are not the only fields and these operators would not know which field should be checked...
How about just: if(c.b_ && c.b_.a_ && c.b_.a_.x) //do smth ... Is that cheating? You can do it all in one 'if' statement this way. I suppose you could write a macro to do something like this: #define CHECK(x,y,z,w) (x.y && x.y.z && x.y.z.w) and then use it like this: if(CHECK(c, b_, a_, x)) //do smth ... And maybe you could write the macro in such a way as to take arbitrary lists of arguments. But that's the best I can come up with. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837
On Thu, August 3, 2006 14:58, james.jones@firstinvestors.com wrote:
From: "Ovanes Markarian"
Now I have an instance of struct C and would like to know if x is a valid pointer. this code is really ugly:
if(c.b_) if(c.b_.a_) if(c.b_.a_.x) //do smth ...
The intention would be to write everything in one if-statement. It is not possible to implement a bool or ! operator in these structures, since these are not the only fields and these operators would not know which field should be checked...
How about just:
if(c.b_ && c.b_.a_ && c.b_.a_.x) //do smth ...
Is that cheating? You can do it all in one 'if' statement this way. I suppose you could write a macro to do something like this:
#define CHECK(x,y,z,w) (x.y && x.y.z && x.y.z.w)
and then use it like this:
if(CHECK(c, b_, a_, x)) //do smth ...
And maybe you could write the macro in such a way as to take arbitrary lists of arguments. But that's the best I can come up with.
- James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837 _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
James, thanks for your answer. This seems to be the possibly best solution. I will play around with it and see how this can be realized with arbitrary lists. This if is not a really nice solution, since the names of the classes are really long... The problem resides that users have to retype this long names (approx. 20 chars each name). I know that this can be an error source, but anyway it is there an can not be changed. if(c.b_ && c.b_.a_ && c.b_.a_.x) Somehow I forgot, that && is a lazy operation. This seems to be a really nice and elegant solution in my opinion. The only problem is that this is a macro. With Kind Regards, Ovanes Markarian
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Ovanes Markarian