Hi,
I wrote the following macro:
#define COM "
#define GET_VAR_LINE(var, type) COM var = %type COM, varSo, this code :
int main()
{
int x = 0;
printf(GET_VAR_LINE(x, d));
}expands to
int main()
{
int x = 0;
printf(" x = %d ", x);
}Acquired with g++ -E main.cpp
How do I eliminate the spaces at the beginning and the end of
" x = %d " ? Thanks.
Fortunately, you can't define these weird macros.
Macro definition consists of tokens (valid C++ lexical units) - it's so called token-string in the C++ standard. In other words, it's not an arbitrary sequence of characters. No such token as a single quote mark in C++. It starts a string literal - but no string literal on #define COM line...
The answer to OP question: see "token-pasting" operator ##. For example:
#define BEAST(head,body,tail) head##body##tailNo spaces between parts of this (useless) macros...
Back to OP macros:
Are you sure that an inexpressive and unintelligible code with complicated macros is the true indication of a good programmer?
Can anyone tell me the answer? Or if it can not be done?
>Can anyone tell me the answer? Or if it can not be done?
ArkM has beautifully answered your question. Open your mind to see this.
I would again like to point out ArkM's last point: If you are a C++ programmer, you should know that Macros are evil. Look at (http://siddhant3s.uuuq.com/how_to_tell_rusted_cpp/#SECTION00051000000000000000)
and (http://www.parashift.com/c++-faq-lite/inline-functions.html#faq-9.5)
If you are a C programmer, you should not post C related queries in C++ forums.
OK. Let me phrase the question in a different manner:
I am going through a fairly large program written by someone else, and I thought it'd make it easy for me if I can just dump objects right into the log. So,
class Test
{
int x;
...
PrintInfo();
};
would print something like
"variable x = 10" in the log.
Is there a easy way to do this?
class Log
{
public:
Log(const char* fname);
...
static ostream& curr()
{
return Log::flog << Log::timeStamp() << ':';
}
...
private:
static const char* timeStamp();
static ofstream flog;
Log(const Log&);
Log& operator=(const Log&);
};
inline
ostream& Log() { return Log::curr(); }
/// My days are numbered if no macros
#define VAR(var) " "#var" = " << var
class Test
{
int x; ...
...
ostream& logInfo()
{
return Log() << "Test::logInfo:"
<< VAR(x) << VAR(y) //<< ...
<< '\n';
}
};
...
Log() << test.logInfo() << VAR(its.me) << endl;
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