Const in C++

[lilzz]

1)Const func1 (Const ClassA&) Const
Const ClassA& means Class A is read-only. What does the left and right hand Const means?


2)ClassA<0> (handler)(error)
what does 0 means?

[danjperron]

1-) I think you mean const and not "Const"

The first const tell that the function will be used when the class is const. And the one at the end tell that is a read only function.

This is an example

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#include <iostream>

using namespace std;

class ClassA
{
  public:
    int nValue;
    ClassA() {nValue=1;}
};

class ClassTest
{
 public:
  ClassTest() {Variable1=0;}
  const int func1(const ClassA& A) const { return A.nValue;}
  int func1(const ClassA& A)  {Variable1=2; return A.nValue;}
  int Variable1;
};




int main(void)
{

  const ClassA  MyA;
  const ClassTest MyTest;
  ClassTest MyTest2;

  cout << "=== MyTest" << endl;
  cout << "nValue = "<< MyTest.func1(MyA) << endl;
  cout << "Variable1 =" << MyTest.Variable1 << endl;
  cout << "=== MyTest2" << endl;
  cout << "nValue = "<< MyTest2.func1(MyA) << endl;
  cout << "Variable1 =" << MyTest2.Variable1 << endl;
return 0;
}

And this is the output

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pi@WebPi ~ $ g++ -o test test.cpp
pi@WebPi ~ $ ./test
=== MyTest
nValue = 1
Variable1 =0
=== MyTest2
nValue = 1
Variable1 =2

2-) Integer template could pass parameters

http://stackoverflow.com/questions/4991 ... int-n-mean
your example are hard to decipher since you just put one line.

I hope it helps

Daniel

[NewNewz]

Can I just check, do I have to use const and not Const - does the capitalization matter? Will Const not work?

http://simplenewz.com/2014-07-29/Mainstream/feed/4459

[danjperron]

C/C++, C#, Python, Java , etc... are all case sensitive.

Const is not const unless you do something like #define Const const

ex: nano const.cpp

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#include <iostream>

#define Const const

const int a=2;
Const int b=3;

int  main(void)
{
  std::cout << "a =" << a << std::endl;
  std::cout << "b =" << b << std::endl;
  return 0;
}

compile it using

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g++ -o const const.cpp

Remove the define and try to recompile.


Daniel