How do I obtain the default hash of a user-defined struct

[dnspies]

Thanks,
Actually I'm realizing there's a lot I'm unclear about when it 
comes to default comparison, equality, hashing, etc.

If my struct contains a dynamic array, are the contents of the 
array compared by default, or just the pointers/lengths?

Also, when two arrays are compared for content, are their 
pointers compared first in case they happen to be the same so the 
deep comparison can be shortcut?
Also, how do I obtain the default hash of a dynamic array ('s 
contents)?  Is there one?  I assume there must be since 
associative arrays can take string as a key-type.

To make a struct a valid key type, do I need to implement both 
opCmp and opEquals or just one or the other.  It says on the page 
about Associative Arrays: "The implementation may use either 
opEquals or opCmp or both."  Does that mean it uses whichever one 
is user-defined (or both if they're both user-defined)?  Or does 
it mean the user is responsible for defining both?

Also, it says "Care should be taken so that the results of 
opEquals and opCmp are consistent with each other when the 
struct/union objects are the same or not.", certainly this means 
that if a.opEquals(b), then a.opCmp(b) should be 0, but does the 
converse have to be true?

Is there somewhere I can find information about default operator 
implementations and consistency?