I'm learning C++ from Thinking in C++ by Eckel. I'm trying to solve an
exercise problem. Here is the first part:
Write a program with conditionally-compiled code in main( ), so that
when a preprocessor value is defined one message is printed, but when
it is not defined another message is printed. Compile this code
experimenting with a #define within the program.
My solution:
#include <iostream>
using std::cout;
using std::endl;
int main() {
//#define PI 3.14159
#ifdef PI
cout << "PI is defined." << endl;
#endif
#ifndef PI
cout << "PI is not defined." << endl;
#endif
}
Then:
Then discover the way your compiler takes preprocessor definitions on
the command line and experiment with that.
How can I create preprocessor definitions on the command line? I was
look at the man pages, but all I found was an option for macros. Are
there docs for g++ that are easier to use than the man pages?
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