How to avoid writing more code in a function?

Good afternoon,

Consider the following function:

Code:

---

double calculate(){
  double ret;
  for (int a = 0; a<=10; a++){
    ret = 2*a;
  }
  return ret;
}

---

This is just a hypothetical function where a variable (here, ret) constantly changes its value.
Suppose I need to print the steps of the function; for example, print every value of ret, and put everything between parentheses:

Code:

---

double calculate(){
  double ret;
  printf("(");
  for (int a = 0; a<=10; a++){
    ret = 2*a;
    printf("%d", ret);
  }
  printf(")");
  return ret;
}

---

(codes not tested in a compiler)
So, in a few words, I have a function that makes calculations, and I want to output the result of each step of the calculation to a file. But the problem is that I don't want to "fill" the function with a lot of output functions, like sprintf, printf, fprintf... I just want the function to have the calculation procedure; otherwise, if I need to use the function somewhere else and didn't need the outputs, I would have to erase them all.
Any idea on how I could track and output the steps of the function and keep it "clean" from lines that output to screen/files?
Tell me if I'm not being very clear.
Thank you in advance.

You could introduce a parameter with a default value, and then use the value of that to determine whether you should print anything or not.

Code:

---

double calculate(const bool print = false)

---

For one thing you might use macros, e.g

Code:

---

double calculate()
{
#ifdef VERBOSE_VERSION
    putchar('(');
#endif
  ...etc
}

---

or

Code:

---

#include <iostream>

//#define VERBOSE_VERSION

#ifdef VERBOSE_VERSION
#define OUTPUT_VALUE(n) std::cout << n << ' '
#else
#define OUTPUT_VALUE(n) (void) 0
#endif


double calculate()
{
    OUTPUT_VALUE('(');
    double ret;
    for (int a = 0; a<=10; a++){
        ret = 2*a;
        OUTPUT_VALUE(ret);
    }
    OUTPUT_VALUE(')');
    return ret;
}

int main()
{
    calculate();
}

---

In general, I think that's what the debugger is for.

Thank you for the help.
Macros seem a good idea; I've never used them. I will try and ask here if something goes wrong.
The only problem is that it would still "pollute" the calculation code a little.
anon: yes, that's what the debugger is for, but, actually, debugging is not my intention.

Quote:

---

Originally Posted by pc2-brazil

debugging is not my intention.

---

Then what is your intention?

Alternatively you could have the function call out to an IOutput interface.

Code:

---

class IOutput
{

public:

virtual ~IOutput() { }
virtual void OutputString(const std::string &text) = 0;

};

double calculate(IOutput *pOutput)
{
    pOutput->OutputString("(");
    std::ostringstream ostrm;
    double ret;
    for (int a = 0; a<=10; a++)
    {
        ret = 2*a;
        ostrm << ret << std::endl;
        pOutput->OutputString(ostrm.str());
        ostrm.str("");
    }
    pOutput->OutputString(")");
    return ret;
}

---

Now the function could care less about how the output is implemented. As long as the object passed in derives from IOutput and implements OutputString() it could output to a disk, monitor, printer, etc, etc and the function body never has to change.