compiling error "conversion from ‘int’ to non-scalar type"
in [C++]
|
Prev: Is there any standard/guarantees for exception safety in STL operations?
Next: Static Analysis Test-Sourcecode ?
From: Bhushan Kakulte on 19 Jul 2010 23:00 While compiling .cc file i got following error p2p/p2pjxta.cc:41: error: conversion from 'int' to non-scalar type 'std::_List_iterator<Neighbor*>' requested p2p/p2pjxta.cc:42: error: conversion from 'int' to non-scalar type 'std::_List_iterator<Neighbor*>' requested p2p/p2pjxta.cc:43: error: conversion from 'int' to non-scalar type 'std::_List_iterator<Neighbor*>' requested original code is: list<Neighbor*>::iterator neigh = NULL; list<Neighbor*>::iterator lowerNeigh = NULL; list<Neighbor*>::iterator upperNeigh = NULL; Also I am facing error p2p/p2pjxta.cc:59: error: no match for 'operator!=' in 'neigh != 0' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../../include/c++/4.1.2/ bits/stl_list.h:173: note: candidates are: bool std::_List_iterator<_Tp>::operator!=(const std::_List_iterator<_Tp>&) const [with _Tp = Neighbor*] p2p/p2pjxta.cc: In member function 'bool P2PJxtaApp::jxtaLookup(P2PAppData*)': for original code if (neigh != NULL) Please help me out..... Thanks -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Nick Hounsome on 20 Jul 2010 04:08 On 20 July, 15:00, Bhushan Kakulte <b.kaku...(a)gmail.com> wrote: > While compiling .cc file i got following error > > p2p/p2pjxta.cc:41: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > p2p/p2pjxta.cc:42: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > p2p/p2pjxta.cc:43: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > > original code is: > > list<Neighbor*>::iterator neigh = NULL; > list<Neighbor*>::iterator lowerNeigh = NULL; > list<Neighbor*>::iterator upperNeigh = NULL; You're not getting iterators at all. a list iterator isn't a pointer (at least not so that you can see and certainly not Neighbour* and since there is no such thing as a null iterator there can be no meaningful comparison to nullptr or or int. The closest you have to null is the result of end() or cend() on yout list<Neighbour> and even then it is only valid for one list and only whilst it isn't modofied -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Daniel Krügler on 20 Jul 2010 04:04 On 20 Jul., 16:00, Bhushan Kakulte <b.kaku...(a)gmail.com> wrote: > While compiling .cc file i got following error > > p2p/p2pjxta.cc:41: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > p2p/p2pjxta.cc:42: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > p2p/p2pjxta.cc:43: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > > original code is: > > list<Neighbor*>::iterator neigh = NULL; > list<Neighbor*>::iterator lowerNeigh = NULL; > list<Neighbor*>::iterator upperNeigh = NULL; The error message says it all: You cannot assign NULL to the specific iterator. This is just normal, because list<Neighbor*>::iterator satisfies the requirements for an iterator. You mix mix up this with a pointer, but iterators are generalizations of pointers and among the iterator requirement does not exist a conversion from int. A reasoanble initial value could be the end() iterator value (if you have a container nearby) which can be interpreted as "end-of-sequence". > Also I am facing error > > p2p/p2pjxta.cc:59: error: no match for 'operator!=' in 'neigh != 0' > /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../../include/c++/4.1.2/ > bits/stl_list.h:173: note: candidates are: bool > std::_List_iterator<_Tp>::operator!=(const std::_List_iterator<_Tp>&) > const [with _Tp = Neighbor*] > p2p/p2pjxta.cc: In member function 'bool > P2PJxtaApp::jxtaLookup(P2PAppData*)': > > for original code > > if (neigh != NULL) Same problem: There does not exist a NULL state for iterators. The most probable equivalent is to use the end() value of a corresponding container. HTH & Greetings from Bremen, Daniel Kr�gler -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: red floyd on 20 Jul 2010 04:07
On Jul 20, 7:00 am, Bhushan Kakulte <b.kaku...(a)gmail.com> wrote: > While compiling .cc file i got following error > > p2p/p2pjxta.cc:41: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > p2p/p2pjxta.cc:42: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > p2p/p2pjxta.cc:43: error: conversion from 'int' to non-scalar type > 'std::_List_iterator<Neighbor*>' requested > > original code is: > > list<Neighbor*>::iterator neigh = NULL; > list<Neighbor*>::iterator lowerNeigh = NULL; > list<Neighbor*>::iterator upperNeigh = NULL; > > Also I am facing error > > p2p/p2pjxta.cc:59: error: no match for 'operator!=' in 'neigh != 0' > /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../../include/c++/4.1.2/ > bits/stl_list.h:173: note: candidates are: bool > std::_List_iterator<_Tp>::operator!=(const std::_List_iterator<_Tp>&) > const [with _Tp = Neighbor*] > p2p/p2pjxta.cc: In member function 'bool > P2PJxtaApp::jxtaLookup(P2PAppData*)': Repeat after me: "An Iterator is not necessarily a pointer". You can't assign an iterator to NULL. What are you actually trying to accomplish? -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] |