Hi,
I have small question
1. i have heard one should never use #defines
in c++. is it true ? if yes why ?
2. if 1) is true then if i use const instead of #define
wont it be more constly because #define
will be replaced at compiler stage
whereas const will occupy memory(read-only)
or is compiler( i am using cfront one)
every time intellegent enough to replace it
based on context.

Thanks

To answer your questions:

1. The reason you should use const instead of #define is
that const can be type checked by the compiler, which
is not the case with #define . This allows you to use
the full power of the C++ compiler to help you find
bugs during compilation, which is much better than
during runtime.

2. According to B. Stroupstrup (The C++ Programming
Language, Third Edition, pp. 95), the compiler
can take advantage of an object being constant and
just replace the object with its value, thereby saving
the space it would otherwise have to allocate. Check the
cfront documentation to see if they take advantage of
this.

Good luck!

-Mart311

Yes I agree with Mart311. But both the methods have some pros and cons.
Advantages of #defines :
1) It enhances the readability of the program
1) #defines are preprocessor directives. So usage of this reduces the burden from the compiler. For eg,
#define MAX 100
........
char str[MAX}.

Then whenever you want to change the size of your array. You need to change at one place only. Whereas if you use const word like
const int x=100;
char str[x];
So x becomes a variable and compiler has to take care of this . Moreover if you look on the code below . Although you've declare i as a constant variable but even then you can change the value be redirecting by a pointer. Just compile this in unix .

const int i = 100;
int *x = &i;
*x = 10;
printf("now the value of i = %d",i);


Disadvantages :
As already mentioned by Mart311

So it depends on your requirement . When and what to use.

Does it answer you question ?
Thanx
Siddhartha Singh
ssingh@aztecsoft.com