Re: declare a struct with c++ vectors in a header file...

From:
beet <whhggg@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 17 Jun 2008 13:23:34 -0700 (PDT)
Message-ID:
<7f7fccc8-41d8-4210-9654-47b820da3987@y38g2000hsy.googlegroups.com>
On Jun 17, 1:17 pm, "Alf P. Steinbach" <al...@start.no> wrote:

* beet:

On Jun 16, 11:28 pm, "Alf P. Steinbach" <al...@start.no> wrote:

* Eric Pruneau:

* "beet" <whh...@gmail.com>:

I tried to declare a c++ struct like following in a header file:
------
     1 #ifndef _SEARCHDATA_H_
     2 #define _SEARCHDATA_H_

Never define names starting with underscore followed by uppercase lette=

r.

Those are reserved for the C++ implementation.

That also goes for use of double underscore.

     3
     4 #include <vector>
     5 #include <list>
     6

add :
using namespace std;
or you gonna have to be type 'std::vector' instead of just 'vector'.
vector (list too) is a class inside the namespace std.

I'm sorry, but that is extremely bad advice.

Never add "using namespace std;" in a header file. It will force unqual=

ified

names from the standard library, on all code that uses the header file.=

 And in

particular, "string" and "vector" are commonly used names for other thi=

ngs than

the standard library classes, and you really don't want to screw up thi=

ngs for

code that uses those names -- that's why the standard library use=

s "std::".

Conversely, when you see "using namespace std;" in a header file then y=

ou know

that the author is incompetent or an utter novice.

Cheers, & hth.,

- Alf

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?


Please don't quote signatures.

Thanks for your replies...
I modified a bit my code according to your comments, but it seems
problems with declaration of functions:

g++ -Wall -g -c searchData.cpp
searchData.cpp: In function `int searchPt(std::vector<int,
std::allocator<int> >&, searchIter&, double&, double&)':
searchData.cpp:46: warning: comparison between signed and unsigned
integer expressions


This is from code you haven't shown. It's just a warning but you should fi=

x it.

  Typical fix to is use 'size_t' for a loop variable.

g++ -Wall -g -o runinv functionfile.o retroSearch.o searchData.o
simlib.o myinv.o mxCalc.o optSolver.o
optSolver.o(.text+0x1d27): In function `egSearch(std::vector<double,
std::allocator<double> >&, double, float&, double&, searchIterInfo&,
float)':
/home/wang75/myResearch/generic/simContSearch/optSolver.cpp:351:
undefined reference to `getInitStep(std::vector<double,
std::allocator<double> > const&, std::vector<double,
std::allocator<double> >&, int, float, int)'


This an undefined reference because the message says "undefined reference"=

..

That means the object files you're linking don't have an implementation of=

 that

function.

Probably it's due to a signature mismatch for something you think is an
implementation.

optSolver.o(.text+0x1ffb):/home/wang75/myResearch/generic/
simContSearch/optSolver.cpp:382: undefined reference to
`getInitStep(std::vector<double, std::allocator<double> > const&,
std::vector<double, std::allocator<double> >&, int, float, int)'
optSolver.o(.text+0x4039): In function `fcn(std::vector<double,
std::allocator<double> > const&, std::vector<double,
std::allocator<double> >&, double, searchIterInfo&, int, int, float)':
/home/wang75/myResearch/generic/simContSearch/optSolver.cpp:711:
undefined reference to `simplexInterp(std::vector<double,


"undefined reference"

std::allocator<double> > const&, std::vector<std::vector<int,
std::allocator<int> >, std::allocator<std::vector<int,
std::allocator<int> > > >&, std::vector<double, std::allocator<double>

&, std::vector<int, std::allocator<int> >&, int, float, int)'

optSolver.o(.text+0x465c): In function `fcnPart(std::vector<double,
std::allocator<double> > const&, std::vector<double,
std::allocator<double> >&, double, int, searchIterInfo&, int, int,
float)':
/home/wang75/myResearch/generic/simContSearch/optSolver.cpp:768:
undefined reference to `simplexInterp(std::vector<double,


"undefined reference"

std::allocator<double> > const&, std::vector<std::vector<int,
std::allocator<int> >, std::allocator<std::vector<int,
std::allocator<int> > > >&, std::vector<double, std::allocator<double>

&, std::vector<int, std::allocator<int> >&, int, float, int)'

collect2: ld returned 1 exit status
make: *** [runinv] Error 1

shell returned 2

----my code ---

      1 #ifndef _searchData_
      2 #define _searchData_


Generally only use ALL UPPERCASE for macro names, and never use that conve=

ntion

for other names, so as to avoid possible name collisions (macros don't res=

pect

scopes) -- this is a FAQ.

I should have been less specific about underscore advice.

As a rule, never use any leading underscore whatsoever, because in the glo=

bal

namespace those names are reserved for the implementation, and it's easies=

t to

just never use them rather than remember where they're not reserved.

      3 #include <vector>
      4 #include <list>
      5
      6 typedef struct searchIterInfo {


This is a C-ism, not necessary in C++. The C construct

   typedef struct { blah blah } SomeName;

is, in C++, better expressed as

   struct SomeName { blah blah };

      7 searchIterInfo ():
      8 contPts(0), //continuous trial points
      9 contFvs(0), //fv for cont points
     10 contFerrors(0), //std errors for cont points
     11 gradients(0), //list of gradients
     12 intPts(0), //evaluated int points
     13 intFvs(0), //function values for in=

t points

     14 intFerrors(0), //errors for int points
     15 intPtList(0), //the monotone list of point=

s

     16 simList(0), //the simplex list
     17 seedVals(0), //the seed values
     18 hMtx(0) {}; //the estimated hesian mat=

rix

Extraneous semicolon after right brace.

Anyway you don't need to define the vector initializations because they're=

 what

you get by default. :-)

What you do need to initialize is what you've forgotten to initialize, nam=

ely

the members of built-in type 'iterID' and 'sampleSize': since they're not =

of

class type they don't have automatic default initialization.

     19
     20 std::vector< std::vector<double> > contPts;
     21 std::vector<double> contFvs;
     22 std::vector<double> contFerror=

s;

     23 std::vector< std::vector<double> > gradients;
     24 std::vector< std::vector<int> > intPts;
     25 std::vector<double> intFvs;
     26 std::vector<double> intFerrors=

;

     27 std::list<int> intP=

tList;

     28 std::list<int> simL=

ist;

     29 std::vector<int> seedVa=

ls;

     30 std::vector< std::vector<double> > hMtx;
     31 int iterID; //the sample path =

index

     32 double sampleSize; //the sample size for th=

is sp

Since the above doesn't communicate any purpose to me, it probably will no=

t

communicate any purpose to you either when you have been away from the cod=

e for

some time. So better more self-describing names would probably be a good i=

dea.

It's also possible, but by no means sure, that you're doing an unnecessary=

inversion of data structure, using a struct of vectors when problem domain=

 calls

for a vector of structs -- generally a struct of like vectors indicate tha=

t. :-)

     33 } searchIter;
     34
     35 std::vector<int> getBestIntPt(searchIter &);
     36 int searchPt(std::vector<int> &, searchIter &, double &,
double &);
     37 void addPt(std::vector<int> &, searchIter &, double fv, do=

uble

fr);
     38
     39 #endif


Cheers, & hth.,

- Alf

- Show quoted text -


Thanks Alf,

the functions are declared and defined in simInterp.h and
simInterp.cpp respectively:
----code---

#ifndef __SIMINTERP_H__
#define __SIMINTERP_H__

void getBinary(int, vector<int> &, int);
int getDecimal(vector<int> &);
void simplexInterp(vector<double> const&, vector< vector<int> > &,
vector<double> &,
   vector<int> &, int = 0, float = 1.0, int = 0);
double getInitStep(const vector<double>&, vector<double> &, int = 0,
float = 1.0, int = 0);

#endif
*****

#include "simInterp.h"
#include <vector>
#include <iostream>
#include <math.h>
void simplexInterp(vector<double> const& x, vector< vector<int> >
&simVerts, vector<double> &wts,
      vector<int> &permu, int simCode, float csize, int patCode)
{
...
}

double getInitStep(const vector<double> &x, vector<double> &d, int
simCode, float csize, int bMax)
{
....
}

-----end of code---

I cannot find anything wrong here.

again, thank you very much for your kind help.

Beet

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