On 6/23/20 5:15 AM, WebFreak001 wrote:
I have the following code:
double[string] foo;
foo["a"] += 1;
how is the opOpAssign on the AA defined? Is it defined to set the value
to the value to the right of the opOpAssign if it isn't set for
primitives or does it add the given value onto T.init?
Doing
foo["b"]++;
gives me 1, so this looks like it comes from an arbitrary 0, however
when I do
double v = foo["c"]++;
I wanted to find out what initial value it is basing the increment off,
however on dmd this triggered a segfault and on ldc this gave me 0.
Where did the 0 come from? double.init should be NaN
I agree. I don't think it's defined by the language, but by the
implementation.
Looking at the implementation, it's here:
https://github.com/dlang/druntime/blob/2cc13ead1e7e535ef8ebd1f600d4ffb508a93f98/src/rt/aaA.d#L502-L577
Note the statement "[Returns:] If key was not in the aa, a mutable
pointer to newly inserted value which is set to all zeros"
This is specifically where the zeroing happens:
https://github.com/dlang/druntime/blob/2cc13ead1e7e535ef8ebd1f600d4ffb508a93f98/src/rt/aaA.d#L220
IIUC, this is a direct binding from the language, so we may not have the
ability to set to init value in object.d, it would have to be done here.
-Steve
