On Saturday, 11 August 2012 at 05:41:23 UTC, Walter Bright wrote:
On 8/10/2012 9:55 PM, F i L wrote:
On the first condition, without an 'else z = ...', or if the
condition was removed at a later time, then you'll get a
compiler error and be forced to explicitly assign 'z'
somewhere above using it. So C# and D work in "similar" ways
in this respect except that C# catches these issues at
compile-time, whereas in D you need to:
1. run the program
2. get bad result
3. hunt down bug
However, and I've seen this happen, people will satisfy the
compiler complaint by initializing the variable to any old
value (usually 0), because that value will never get used.
Later, after other things change in the code, that value
suddenly gets used, even though it may be an incorrect value
for the use.
Note to Walter:
You're obviously correct that you can make an arbitrarily complex
program to make it too difficult for the compiler to enforce
initialization, the way C# does (and gives up in some cases).
What you seem to be missing is that the issue you're saying is
correct in theory, but too much of a corner case in practice.
C#/Java programmers ___rarely___ run into the sort of issue
you're mentioning, and even when they do, they don't have nearly
as much of a problem with fixing it as you seem to think.
The only reason you run into this sort of problem (assuming you
do, and it's not just a theoretical discussion) is that you're in
the C/C++ mindset, and using variables in the C/C++ fashion.
If you were a "C#/Java Programmer" instead of a "C++ Programmer",
you simply _wouldn't_ try to make things so complicated when
coding, and you simply _wouldn't_ run into these problems the way
you /think/ you would, as a C++ programmer.
Regardless, it looks to me like you two are arguing for two
orthogonal issues:
F i L: The compiler should detect uninitialized variables.
Walter: The compiler should choose initialize variables with NaN.
What I'm failing to understand is, why can't we have both?
1. Compiler _warns_ about "uninitialized variables" (or scalars,
at least) the same way C# and Java do, __unless__ the user takes
the address of the variable, in which case the compiler gives up
trying to detect the flow (like C#).
Bonus points: Try to detect a couple of common cases (e.g.
if/else) instead of giving up so easily.
2. In any case, the compiler initializes the variable with
whatever default value Walter deems useful.
Then you get the best of both worlds:
1. You force the programmer to manually initialize the variable
in most cases, forcing him to think about the default value. It's
almost no trouble for
2. In the cases where it's not possible, the language helps the
programmer catch bugs.
Why the heck D avoids #1, I have no idea.
It's one of the _major_ features of C# and Java that help promote
correctness, and #1 looks orthogonal to #2 to me.
For users who don't like #1: They can suppress the warning.
Nothing lost, anyway.
For users who DO like #1: They can turn it into an error. A lot
to be gained.
