The thing you have to remember is that every
int conversion and vice versa potentially loses information. On most implementations,
int can store a larger integer number with full precision than
float's decimal values are chopped off when converting to an
int and that
float can store larger numbers than can fit into an
Now for your specific use case, that may be perfectly fine or more specifically is exactly what you want. But in general, one should not take such conversions lightly.
Consider just the example from your SO question, which doesn't even involve
int size = vector.size(); // Throws an implicit conversion warning
int size = (int)vector.size(); // C like typecasting is discouraged and forbidden in many code standards
int size = static_cast<int>vector.size(); // This makes me want to gauge my eyes out (it's ugly)
Each of these cases has a subtle bug: if the size of the
vector is greater than
numeric_limits<int>::max() (typically 2^31 - 1), then you aren't getting the actual size. So whatever you're doing with
size is not going to work.
Now, you can say that you won't have a
vector that big. And that may genuinely be true... today. How many security holes/bugs have been opened up because an application scaled to the point where some value overflowed the expected type? And how many bugs exist that are out there, lurking, waiting to pounce once some arbitrary size is exceeded?
That's why you get a warning when you don't explicitly convert it. That's why C++ uses syntax that "makes me want to gauge my eyes out". It's because what you're doing may not be safe. So you should carefully consider whether you ought to be doing it.
And that's where we get to:
3D voxelization of geometry; 3D reconstruction of 2D textures and subsequent UV mapping onto the original texture to store values; Conversion of float coordinates to grid cells for the cached version of perlin noise...
Each of those things should be hidden behind some interface which internally does the required conversion. And not a simplistic
convert_int function; I mean one that is specific to the task in question. If you're converting normalized [0, 1] floats into pixel coordinates for a texture of some size, you have a function to do exactly that. It would be given the coordinates and the size of the texture, and it would return integer coordinates.
The point of the advice is that your code should not be littered with such naked conversions.