Thread: convert return value to a pointer

Originally Posted by jeanluca

this is actually not a one-liner

Unlike in some other contexts, C and C++ programmer's are not hot about the "all-in-one-liner"; possibly this is because the language does not really lend itself to that concept very well. just to let you know

Unless you want to write a function to do it:

Code:

float *my_atof(char *string) {
      float *ptr = malloc(sizeof(float));
      *ptr = atof(string);
      return ptr;
}

Now:

Code:

float *x = my_atof("12.13");

which might be handy if you have to do it enough times, and you really need a pointer that can be passed around *and* modified (if you do not need to change this value later, you do not need a pointer).

Remember to free() pointers you have malloc'd when you are done with them:

Code:

free(ptr);
ptr=NULL;

B/T/W: The newer C99 function strtof() would be considered safer and more portable than atof().

The return value of a function doesn't (necessarily) have an address. So using the & operator on such a value won't work. For example, in x86, the float may well reside in st(0) - the top of the floating point register stack. This register, obviously, isn't a memory location, so thus doesn't have an address. Similarly if you have an integer return value, it will be in eax. Again, it has no address.

You obviously can't make a pointer to something that doesn't have an address!

--
Mats

I think it's rather unlikely that you need a pointer in the first place. Maybe you might pass a pointer to a function, so that the function can assign a value to the parameter; but then you'd call the function with the address of the variable you want it to fill, like so:

Code:

int x;
func(&x);

void func(int *x) {
    *x = 5;
}

I can't see why you'd need to do what you are describing. Can you describe your problem in more detail?

[edit]

Unlike in some other contexts, C and C++ programmer's are not hot about the "all-in-one-liner"; possibly this is because the language does not really lend itself to that concept very well.

Uh huh. How many times have you seen code like this?

Code:

void Stack::push(Type data) { stack[top ++] = data; }
while(*p++ == *q ++);
for(p = string; *p && isspace(*p); p ++);
std::cout << "Your answer is " << (correct ? "right" : "wrong") << '.' << std::endl;

I think it's almost as bad as Perl. If you want a language you really can't do one-liners in, try Python.
[/edit]