MESSAGE
| DATE | 2016-11-09 |
| FROM | Ruben Safir
|
| SUBJECT | Re: [Learn] namespace and external files confusion
|
From learn-bounces-at-nylxs.com Wed Nov 9 11:11:45 2016
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From: Ruben Safir
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Date: Wed, 9 Nov 2016 11:11:43 -0500
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Subject: Re: [Learn] namespace and external files confusion
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On 11/09/2016 11:05 AM, Christopher League wrote:
> =
> In the .cpp file, it's not enough to say `using namespace merge`. You
> also want to be *defining* things in that same namespace. Otherwise you
> are defining `::track` but trying to recursively call `merge::track`.
> =
> Change that `using namespace merge` into `namespace merge { ....... }`
> that covers the rest of the definitions.
> =
> That compiles.
> =
I did that finally, just three minutes ago. I didn't know why. There
are so many words in these books on this topic and nothing is clear.
I'm gonna write an FAQ on this if I have time. Meanwhile I have now 5
hours to parralize this and debug it ...
> CL
> =
> Ruben Safir writes:
> =
>> [This mail was also posted to comp.lang.c++.]
>>
>> I'm doing this simple merge sort program and I'm tripping on this error
>>
>> C++ call of overloaded =91track(int*&, int&, int&, int*&)=92 is ambiguous
>>
>> I think this comes down to my confusion with namespace and I'm not
>> finding a good reference with C++
>> on namespace usage in different files
>>
>> I have merge.h
>>
>> #ifndef MSORT_INC
>> #define MSORT_INC
>>
>> namespace merge{
>>
>> int max(int x, int y);
>> void track(int* , int , int , int* );
>> int sort(int &input , int size);
>> }
>> #endif /* ----- #ifndef MSORT_INC ----- */
>>
>>
>> and merge.cpp
>>
>> #include "msort.h"
>>
>> using namespace merge;
>>
>> int max(int x, int y){
>> int ret;
>> x>y ? ret=3Dx : ret=3Dy;
>> return ret;
>> }
>>
>> void track(int* in, int left, int right, int* space)
>> {
>> int i =3D 0;
>> int length =3D right - left;
>> =
>> if(right =3D=3D left + 1){
>> return;
>> }
>> int mpt =3D length/2;
>> int pos1 =3D left;
>> int pos2 =3D left + mpt;
>> int pos3 =3D right;
>> //do the recursion now on the left and right branches
>> track(in, pos1, pos2, space);
>> track(in, pos2, pos3, space);
>> for(i =3D 0; i < length; i++)
>> {
>> if(pos1 < pos2 && ( pos2 =3D=3D pos3 || max(in[pos1], in[pos2]) =3D=
=3D
>> in[pos1]))
>> {
>> space[i] =3D in[pos1];
>> pos1++;
>> }
>> else{
>> space[i] =3D in[pos2];
>> pos2++;
>> }
>> }
>> /* transfer array segment */
>> for(i =3D left; i < right; i++)
>> {
>> in[i] =3D space[i - left];
>> }
>> }
>>
>>
>>
>> And the error I get is
>> C++ call of overloaded =91track(int*&, int&, int&, int*&)=92 is ambiguous
>>
>> gvim sees it right away as well
>>
>>
>> || gcc -M *.cpp >make.deps
>> || g++ -Wall -ggdb -c msort.cpp
>> || msort.cpp: In function =91void track(int*, int, int, int*)=92:
>> msort.cpp|25 col 29| error: call of overloaded =91track(int*&, int&, int=
&,
>> int*&)=92 is ambiguous
>> || track(in, pos1, pos2, space);
>> || ^
>> msort.cpp|11 col 6| note: candidate: void track(int*, int, int, int*)
>> || void track(int* in, int left, int right, int* space)
>> || ^~~~~
>> msort.h|25 col 6| note: candidate: void merge::track(int*, int, int, int=
*)
>> || void track(int* , int , int , int* );
>> || ^~~~~
>>
>>
>> and it seems to identify the definition in the .cpp file as a separate
>> declaration than the declation in the .h file
>> What am I doing wrong?
>>
>>
>>
>> -- =
>> So many immigrant groups have swept through our town
>> that Brooklyn, like Atlantis, reaches mythological
>> proportions in the mind of the world - RI Safir 1998
>> http://www.mrbrklyn.com
>>
>> DRM is THEFT - We are the STAKEHOLDERS - RI Safir 2002
>> http://www.nylxs.com - Leadership Development in Free Software
>> http://www2.mrbrklyn.com/resources - Unpublished Archive
>> http://www.coinhangout.com - coins!
>> http://www.brooklyn-living.com
>>
>> Being so tracked is for FARM ANIMALS and and extermination camps,
>> but incompatible with living as a free human being. -RI Safir 2013
>> _______________________________________________
>> Learn mailing list
>> Learn-at-nylxs.com
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> =
> =
> =
> _______________________________________________
> Learn mailing list
> Learn-at-nylxs.com
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> =
-- =
So many immigrant groups have swept through our town
that Brooklyn, like Atlantis, reaches mythological
proportions in the mind of the world - RI Safir 1998
http://www.mrbrklyn.com
DRM is THEFT - We are the STAKEHOLDERS - RI Safir 2002
http://www.nylxs.com - Leadership Development in Free Software
http://www2.mrbrklyn.com/resources - Unpublished Archive
http://www.coinhangout.com - coins!
http://www.brooklyn-living.com
Being so tracked is for FARM ANIMALS and and extermination camps,
but incompatible with living as a free human being. -RI Safir 2013
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