boost::shared_ptr and NULL
In this function declaration, is there a simpler way to express a null shared pointer as the default argument value? void foo( const boost::shared_ptr<T> & p = boost::shared_ptr<T>( ) ); In this function call, is there a simpler way to express a null shared pointer as the actual argument? foo( boost::shared_ptr<T>( ) ); ----------------------------------------------------------------------- Andrew R. Thomas-Cramer Work: artc@prism-cs.com http://www.prism-cs.com/ Home: artc@execpc.com http://www.execpc.com/~artc/ ----------------------------------------------------------------------- [Non-text portions of this message have been removed]
From: "Andrew R. Thomas-Cramer" <artc@prism-cs.com>
In this function declaration, is there a simpler way to express a null
void foo( const boost::shared_ptr<T> & p = boost::shared_ptr<T>( ) );
In this function call, is there a simpler way to express a null shared
shared pointer as the default argument value? pointer as the actual argument?
foo( boost::shared_ptr<T>( ) );
No to both. In 1.27 boost::shared_ptr can be constructed from the literal 0, but the constructor is explicit. In 1.28, the literal 0 is no longer a valid argument to the constructor.
----- Original Message ----- From: "Peter Dimov" <pdimov@mmltd.net> To: <Boost-Users@yahoogroups.com> Sent: Monday, May 13, 2002 1:44 PM Subject: Re: [Boost-Users] boost::shared_ptr and NULL
Has there been any discussion in the past about supporting a more concise/readable value? E.g., the second call below appears more readable to me. (This particular example relies on "boost::null" being a class with a default constructor, and boost::shared_ptr providing a non-explicit constructor accepting a boost::null instance as an argument; this may be flawed.) foo( boost::shared_ptr<MyVeryLongClassName>() ); foo( boost::null() );
From: "Andrew R. Thomas-Cramer" <artc@prism-cs.com>
Has there been any discussion in the past about supporting a more concise/readable value? E.g., the second call below appears more readable
to me.
No, I don't recall any discussion about it. I haven't encountered this problem myself; I typically overload foo so that the call would be simply foo(); This doesn't extend well to multiple optional shared_ptr arguments, of course.
As an alternative, I usually find that the "Introduce Null Object" refactoring results in simpler and more readable code overall. Perhaps not as concise though. ----- Original Message ----- From: Andrew R. Thomas-Cramer To: Boost-Users@yahoogroups.com Sent: Monday, May 13, 2002 12:50 PM Subject: Re: [Boost-Users] boost::shared_ptr and NULL ----- Original Message ----- From: "Peter Dimov" <pdimov@mmltd.net> To: <Boost-Users@yahoogroups.com> Sent: Monday, May 13, 2002 1:44 PM Subject: Re: [Boost-Users] boost::shared_ptr and NULL
Has there been any discussion in the past about supporting a more concise/readable value? E.g., the second call below appears more readable to me. (This particular example relies on "boost::null" being a class with a default constructor, and boost::shared_ptr providing a non-explicit constructor accepting a boost::null instance as an argument; this may be flawed.) foo( boost::shared_ptr<MyVeryLongClassName>() ); foo( boost::null() ); Yahoo! Groups Sponsor ADVERTISEMENT Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]
As an alternative, I usually find that the "Introduce Null Object" refactoring results in simpler and more readable code overall. Perhaps not as concise
----- Original Message ----- From: "Sean Shubin" <sshubin@socal.rr.com> To: <Boost-Users@yahoogroups.com> Sent: Tuesday, May 14, 2002 3:25 AM Subject: Re: [Boost-Users] boost::shared_ptr and NULL though. I'm not familiar with that term. Could you define it and provide an example?
From the book "Refactoring"
As an alternative, I usually find that the "Introduce Null Object" refactoring results in simpler and more readable code overall. Perhaps not as concise
Sometimes you can simplify a conditional expression such as this: class Foo { void foo() { ... } }; ... x = 0; ... if(x == 0) handleNullCondition(); //conditional expression else x->foo(); with something like this: class Foo { void foo() { ... } }; class NullFoo { void foo() { handleNullCondition(); } }; ... x = new NullFoo(); //instead of x = 0 ... x->foo(); //conditional expression goes away //polymorphism handles it instead So if I only have one check for class Foo being null, the code becomes bigger (I create a new class). But if I had many checks all over the place, it actually simplifies the code (a lot of if statements go away). ----- Original Message ----- From: Andrew R. Thomas-Cramer To: Boost-Users@yahoogroups.com Sent: Tuesday, May 14, 2002 7:11 AM Subject: Re: [Boost-Users] boost::shared_ptr and NULL ----- Original Message ----- From: "Sean Shubin" <sshubin@socal.rr.com> To: <Boost-Users@yahoogroups.com> Sent: Tuesday, May 14, 2002 3:25 AM Subject: Re: [Boost-Users] boost::shared_ptr and NULL though. I'm not familiar with that term. Could you define it and provide an example? Yahoo! Groups Sponsor ADVERTISEMENT Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]
participants (3)
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Andrew R. Thomas-Cramer -
Peter Dimov -
Sean Shubin