On 14/04/12 16:52, F i L wrote:
The initialization values chosen are also determined by the underlying
hardware implementation of the type. Signalling NANs
(http://en.wikipedia.org/wiki/NaN#Signaling_NaN) can be used with floats
because they are implemented by the CPU, but in the case of integers or
strings their aren't really equivalent values.
I'm sure the hardware can just as easily signal zeros.
The point is not that the hardware can't deal with floats initialized to zero.
The point is that the hardware CAN'T support an integer equivalent of NaN. If
it did, D would surely use it.
Like I said before, this is backwards thinking. At the end of the day, you
_can_ use default values in D. Given that ints are defaulted to usable values,
FP Values should be as well for the sake of consistency and convenience.
Speaking as a new user (well, -ish), my understanding of D is that its design
philosophy is that _the easy thing to do should be the safe thing to do_, and
this concept is pervasive throughout the design of the whole language.
So, ideally (as bearophile says) you'd compel the programmer to explicitly
initialize variables before using them, or explicitly specify that they are not
being initialized deliberately. Enforcing that may be tricky (most likely not
impossible, but tricky, and there are bigger problems to solve for now), so the
next best thing is to default-initialize variables to something that will scream
at you "THIS IS WRONG!!" when the program runs, and so force you to correct the
error.
For floats, that means NaN. For ints, the best thing you can do is zero. It's
a consistent decision -- not consistent as you frame it, but consistent with the
language design philosophy.
You can't force new D programmers to follow a 'guidline' no matter how loudly
the documentation shouts it
No, but you can drop very strong hints as to good practice. Relying on default
values for variables is bad programming. The fact that it is possible with
integers is a design fault forced on the language by hardware constraints. As a
language designer, do you compound the fault by making floats also init to 0 or
do you enforce good practice in a way which will probably make the user
reconsider any assumptions they may have made for ints?
Novice programmers need support, but support should not extend to pandering to
bad habits which they would be better off unlearning (or never learning in the
first place).
