AA with dynamic array value

[ketmar via Digitalmars-d-learn]

On Wednesday, 6 July 2016 at 02:19:47 UTC, Craig Dillabaugh wrote:
> Why doesn't my function allow me to insert elements into an 
> empty associative array, but succeeds for an AA with some 
> element in it?

this is true for any dynamic array, including AAs. until 
something is added to array, it actually a `null` pointer. i.e. 
arrays (and AAs) generally consisting of pointer to data and some 
length/info field. while array is empty, pointer to data is 
`null`. and when you passing your dynamic array slice/AA to 
function, it makes a copy of those internal fields. reallocing 
`null` doesn't affect the original variable.

generally speaking, you should use `ref` if you plan to make your 
dynamic array/AA grow. i.e.

  void insertValue (ref int[][string]aa, string key, int value)