Declaring a Constructor

[Crippy]

Hello There!
I'm working on a histogram class, but something seems to be wrong with the constructor I'm using...

here's the code:

class histo
{
      private:
              int nBin_p;       
              float min_p, max_p; 
              int *BinContent_p;
              float step_p;
              float sum_p;      
      
      public:
            histo();       //default constructor  
            histo(int &nBin, float &min, float &max);      //constructor
            ~histo();              //destructor
            
            int fill(const float &val);
            void print()const;
            float getMean()const;
            
};


histo::histo(int &nBin, float &min, float &max)
{
            nBin_p=nBin;
            min_p=min;
            max_P=max;         
            step_p=(max_p-min_p)/nBin_p;
            sum_p=0.;
            BinContent_p=new int[nBin_p];
            for (int i=0; i<nBin_p; i++)
                BinContent_p[i]=i;  
                
}

histo::~histo()
{
               delete BinContent_p[nBin_p];
}

I get an error message at line 12 saying:
" expected `,' or `...' before ';' token "
" expected `)' before ';' token "
"expected unqualified-id before "const" "

is it just a semicolon mistake somewhere? or am i getting const correctness wrong??

[Disch]

This is unrelated to your problem, but you should not be passing by reference. The constructor should look like this:

histo(int nBin, float Min, float Max);

note I got rid of the &'s.

As for your error... are you #including <windows.h>? If yes, it #defines min and max, which means you can't use those as identifiers in your code. Note I changed the names above to 'Min' and 'Max' to avoid this conflict.

[Crippy]

Thanks!!

why shouldn't I pass references though?

[Crippy]

Ps...I only #included <iostream>

[Albatross]

Generally one passes by reference in one of two cases: to save large amounts of space by avoiding the copying of a large variable (in which case a const is generally used for safety reasons), or if there's an intention of changing a variable being passed to the function. Neither appears to apply here, so there's no real need to pass by reference. :)

-Albatross

[Crippy]

Thank you!
my compiler still refuses to look at it though...any idea as to why?
I tried changing min, max to Min, Max, but it still won't work..

[Crippy]

Is something wrong with the declaration of the constructor?

[firedraco]

Did you change them in both places? (the class and the definition)

What is the exact error you are getting?

[coder777]

Is something wrong with the declaration of the constructor?

no. I can compile it. But line 26 and 37 are wrong

[Crippy]

ok!.. I thought 37 wasn't right...it should jut be:

delete BinContent_p;

right?

But why is line 26 wrong? in that case, are 24 and 25 wrong too?

the errors I get are:

" expected `,' or `...' before ';' token "
" expected `)' before ';' token "
"expected unqualified-id before "const" "

both referred to line 12

[firedraco]

Could you paste the code as you have it now?

Oh, and if you use new[] you need to use delete[] to match, just a normal delete doesn't work:

delete [] BinContent_p;

[Crippy]

Also, I'm writing all this in a header file, and i wrote this:

#include<iostream>
using namespace std;

#ifndef histo_h
#define histo_h

class histo
{....

Is Something wrong about this??I'm not very confident about using header files yet...

[Crippy]

Ok...this is the code as I have i now:

#ifndef histo_h
#define histo_h

#include<iostream>
using namespace std;



class histo
{
      private:
              int nBin_p;      
              float min_p, max_p; 
              int *BinContent_p;
              float step_p;
              float sum_p;   
      
      public:
            histo();                                                  //default constructor
            histo(int nBin, float Min, float Max);      //constructor
            ~histo();                                              //destructor
            
            //int fill(const float &val);
            void print()const;
            //float getMean()const;
            
};


histo::histo(int nBin, float Min, float Max)
{
            nBin_p=nBin;
            min_p=Min;
            max_P=Max;         
            step_p=(max_p-min_p)/nBin_p;
            sum_p=0.;
            BinContent_p=new int[nBin_p];
            for (int i=0; i<nBin_p; i++)
                BinContent_p[i]=i;  
                
}

histo::~histo()
{
               delete [] BinContent_p;
}

[Crippy]

Oh...and it's the header file, saved as program-12.h :D

[firedraco]

You seem to be missing an #endif in that file, but I'm guessing that's just a copy/paste error.

As for your code...I don't really see anything wrong.

[Crippy]

yeah...you're right: the #endif was later on...

groaaaaan!!! it still won't compile :(

Thank you any way for your help ;o)

[coder777]

Crippy wrote:

ok!.. I thought 37 wasn't right...it should jut be:

delete BinContent_p;

right?

yes

Crippy wrote:

But why is line 26 wrong? in that case, are 24 and 25 wrong too?

line 26 is wrong because you wrote max_P which should be max_p // note: low case p . line 24/25 are ok.

for line 12. I don't have any explanation other than the compiler is wrong or macros. Try other names

[Crippy]

what do you mean by macros?

[firedraco]

See: http://www.cplusplus.com/doc/tutorial/preprocessor/

[Moschops]

I made two changes to the code posted at 9:42 (added #endif to the end and changed max_P to max_p on line 34) and it compiles without any problem into a library.