Difference between concatenation and appendation

[Laeeth Isharc via Digitalmars-d-learn]

On Monday, 26 January 2015 at 01:17:17 UTC, WhatMeWorry wrote:
> Ok, I just made up that word. But what is the difference 
> between appending and concatenating?  Page 100 of TPDL says 
> "The result of the concatenation is a new array..." and the 
> section on appending talks about possibly needing expansion and 
> reallocation of memory.
>
> But I still don't feel like I have a grasp on the subtleties 
> between them. Can someone give a short and sweet "rule of 
> thumb"?
>
> It might be so obvious that I'll regret posting this.
>
> Thanks.


At the risk of the blind leading the blind (I am no expert), I 
think concatenation and append are used as synonyms (the same 
meaning is meant).  a~=b or a=a~b

If there isn't enough space then the whole array is reallocated.  
You can see this/change this property by reading capacity or 
calling reserve.

If you want to do lots of appends / concatenates then use 
appender in std.array which is faster and more efficient.