Re: test if a string is a valid 'number'?

From:

"Ashot Geodakov" <a_geodakov@nospam.hotmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 31 May 2007 13:41:28 -0700

Message-ID:

<u#seRQ8oHHA.1388@TK2MSFTNGP05.phx.gbl>

I agree with you 95%, with the remaining 5% to the fact, that now, in order
to accomplish a small task that must take no more than 30 lines of code, you
have spawned 5 classes for the FSM and about 15 classes for exceptions, 5
lines of code per each exception class.

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:iaau53tce8mop9msvmb19t6s7pv9b8nmvt@4ax.com...

Generally, you watch for the use of switch to decode and realize that in
most cases,
virtual methods and subclasses are a better solution. Otherwise, you are
writing 1975 C
code in a modern programming language. The problem is that if you add a
new case, you
have to find all the places where you have switch statements and amend
them, whereas if
you use virtual methods, you only have to change the definition site.
joe

On Thu, 31 May 2007 08:44:35 -0700, "Ashot Geodakov"
<a_geodakov@nospam.hotmail.com>
wrote:

class MyException
{
public:
enum { BadSign, IllegalDigit, SoOn } m_type;
};

try
{
.. do stuff
}
catch( MyException* e )
{
  switch( e->type )
  {
   case MyException::BadSign:
     ..message about bad sign.
     break;
  }
  delete e;
}

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:33jt53tirdrl3tb7t7r6m9blu1tfg1o61k@4ax.com...

I'm not sure of the correlation here between the example you gave and
the
example I gave,
but yes, had I chosen that particular style of signaling an error, I
would
use the
exception type so I could issue a meaningful error message. Otherwise,
the exceptions
would all end up reporting "Syntax error", which is not exactly
construable as a
user-friendly interface.
joe

On Wed, 30 May 2007 22:56:18 -0700, "Ashot Geodakov"
<a_geodakov@nospam.hotmail.com>
wrote:

I remember someone I worked with in the past, who loved to create a
class
for each small task.

Instead of just

int a = 2 + 2;

he wrote:

class Sum
{
private:
int result;
public:
Sum( int a, int b ) : result( 0 ) { result = a + b; }
GetResult() { return result; }
};

So, SBadSignException, huh? Is it for the situation when the first
character
in the string is not a digit or "+" or "-"?

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:9gds53t23d6j8mhf1aei6ftnp1h09b0nro@4ax.com...

Whenever I want to throw exceptions to represent problems, I always
create
an abstract
superclass exception, e.g., CLexicalException, then I can derive
subclasses such as
CBadSignException, CIllegalDigitException, and so on. So the caller
knows
that any
exception thrown is always a member of the superclass, and could
create
a
superclass catch
clause to capture the exception.
joe

Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm