Re: += on associative arrays leads to surprising result
On Tuesday, 27 August 2019 at 16:45:53 UTC, Samir wrote: I never understood why the intial value of floats, doubles and reals was NaN. That's for detecting uninitialised variables. If the result of a calculation is NaN, it's likely, that you forgot to initialise the variable.
Re: += on associative arrays leads to surprising result
On Tuesday, 27 August 2019 at 16:12:07 UTC, berni wrote: What's your oppinion on this? As someone relatively new to programming in general and to D in particular, this behavior does, on the surface, seem inconsistent. Good to see that a bug exists for this, per ag0aep6g. I never understood why the intial value of floats, doubles and reals was NaN. Samir
Re: += on associative arrays leads to surprising result
On 27.08.19 18:12, berni wrote:
import std.stdio;
void main()
{
real[int] a;
a[0] += 100;
writeln(a);
}
results (independed of the used compiler) in
[0:100]
I was a little bit surprised, because a[0] += 100 should be the same as
a[0] = a[0]+100, which leads to a range violation error. Furthermore, as
we work with real, I'd expected the result to be NaN...
Is this a bug? I ask, because it would be quite convenient to use it the
way it works now.
For what it's worth, it's in Bugzilla:
https://issues.dlang.org/show_bug.cgi?id=4463
+= on associative arrays leads to surprising result
import std.stdio;
void main()
{
real[int] a;
a[0] += 100;
writeln(a);
}
results (independed of the used compiler) in
[0:100]
I was a little bit surprised, because a[0] += 100 should be the
same as a[0] = a[0]+100, which leads to a range violation error.
Furthermore, as we work with real, I'd expected the result to be
NaN...
Is this a bug? I ask, because it would be quite convenient to use
it the way it works now.
An alternative I found, would be to use object.update. But there
I've to declare the 100 twice which results in code duplication:
a.update(0,()=>100.0L,(ref real v)=>v+100.0L);
Hence, my best solution needs two lines:
if (0 !in a) a[0] = 0;
a[0] += 100;
What's your oppinion on this?
