I'm defining a variable as integer and want to use thati
int specLength = 17;
int spec[specLength-1];
When I do this, I get the following error message:
TestProgram:34: error: array bound is not an integer constant before ']' token
int spec[specLength-1];
But when I set it up as
int specLength = 17;
int spec[16];
it all works fine.
What is the magic here?
Many thanks
You have to use a constant expression, one that produce always the same value.
const int specLength = 17;
int spec[specLength - 1];
Otherwise, the compiler won't know how much space reserve for the array.
The problem with C/C++ is that the compiler doesn't really know if a variable is modified somewhere or not (thru pointers, for example). You have to tell the compiler that something is static, not changing.
You can also use a #define for the same porpuse:
#define SPEC_LENGTH 17
int spec[SPEC_LENGTH]
Why both? const int val=17 means that val has a type (int). Using #define is just a text search-and-replace before compiling. So, SPEC_LENGTH has no type at all. If needed, you have to use a cast, like (int) SPEC_LENGTH.