Changing one character in a char[]

[codegirl]

This is probably a really silly question but I haven't been able to find an answer... But Visual C++ will not let me do the following code (I get a run-time error):

// In header file
char *filename;

// In constructor
filename = "frame0000.tif";

// Later in another method
++filename[8];  // This is where I get the error

How can I can I change one character in a string? MSDN says the above code is illegal (even though I know I've done it in other compilers!) but I can't figure out what to do instead. I've also tried initializing filename using strncpy so it will no longer be constant...

Thanks for your help!

[alphaoide]

What do you want this statement to do?
++filename[8]; You can't increment "char." If you want to change the size, increment the index.
Suggestion: declare "filename" as string and if you want to convert to characters array do "filename.c_string."
If you want to replace n-th character in a string: filename[n] = 'c'

[codegirl]

If filename == "frame0000.tif", then that line of code should set filename to "frame0001.tif." I've even got the old program where I've pulled that trick, but it must have only worked under that compiler. If I can't increment char's, how I can I do this without using a ton of if statements?

[thefroggy]

It is perfectly legal to modify a character in a string like that - however, it is not legal to modify a string constant.

char* str = "hello world";

That code sets str to point to the string literal "hello world" in the read only data segment of your program.

You'll have to malloc some memory and use strcpy(), or use an array.

char* filename = new char[14];
strcpy(filename, "frame0000.tif";
++filename[8];
delete[] filename;

or

char filename[] = "frame0000.tif";
++filename[8];

Personally, I would just use a std::string:

std::string filename("frame0000.tif");
++filename[8];

Hope that helps.

[alphaoide]

I got the question, now, but I guess the thread above answered it. Yup, I would use the last coded myself.