Set null as function array parameter

[Oleg via Digitalmars-d-learn]

On Monday, 12 January 2015 at 15:59:43 UTC, Adam D. Ruppe wrote:
> Why are you using ref? Take that off and you can pass any 
> array, including null, with ease.

Because dynamic arrays are passed by value to functions. Will it 
make another copy of array, if I'll pass array by value?

Looks like it won't (I've checked pointers), but I read in wiki 
(http://en.wikibooks.org/wiki/D_%28The_Programming_Language%29/d2/Strings_and_Dynamic_Arrays#Passing_Dynamic_Arrays_to_Functions) 
that it will copy "structure that contains the -pointer to the 
first element- and the length is copied and passed". Does it mean 
something else? maybe i don't understand it correctly.