On 5/19/2016 1:26 PM, Timon Gehr wrote:
Those two lines producing different results is unexpected, because you are explicitly saying that y is a double, and the first line also does implicit rounding (probably -- on all compilers and targets that will be relevant in the near future -- to double).
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It's obviously bad language design on multiple levels.
Floating point semantics simply are not that simple, on any compiler, language or hardware. I recommend reading what the C/C++ Standards say about it, and look at the plethora of compiler switches for VC++/g++/clang++.
The people who design these things are not fools, and there are good reasons for the way things are.
Sorry, I don't agree.
If you say so. I would like to see an example that demonstrates that the first roundToDouble is required.
That's beside the point. If there are spots in the program that require rounding, what is wrong with having to specify it? Why compromise speed & accuracy in the rest of the code that does not require it? (And yes, rounding in certain spots can and does compromise both speed and accuracy.)
And if you are not? (I find the standard assumption that counterexamples to wrong statements are one-off special cases tiresome.
You might, but I've implemented a number of FP algorithms, and none of them required rounding to a lower precision. I've also seen many that failed due to premature rounding.
Creating useful programs in D shouldn't require knowing (or thinking about) an excess amount of D-specific implicit arcane details of the language semantics. Being easy to pick up and use is a major selling point for D.
As pointed out innumerable times here, the same issues are in C and C++ (with even more variability!). When designing an algorithm that you know requires rounding in a certain place, you are already significantly beyond implementing a naive algorithm, and it would be time to start paying attention to how FP actually works.
I'm curious if you know of any language that meets your requirements. (Java 1.0 did, but Sun was forced to abandon that.)
