• Adrian Matoga (11/11) Jun 16 2010 I needed a duplicate of associative array so I wrote myDict.dup, which
• bearophile (11/13) Jun 16 2010 This is a possible version (untested):
• Adrian Matoga (2/2) Jun 16 2010 I also solved it with foreach but the way you wrapped it into a handy
• dsimcha (14/27) Jun 16 2010 other people have asked for it years before. I think it will be added, b...

Adrian Matoga <epi atari8.info> writes:

I needed a duplicate of associative array so I wrote myDict.dup, which 
failed to compile (I use DMD 2.046). So I looked into the official 
language spec, which doesn't mention "dup" property for associative arrays.
The only trace I found on the Internet is in the preview of 4th chapter 
of TDPL (I'm still waiting for my copy from amazon.co.uk, which I hope 
will be dispatched before August), which, at the top of page 124, 
claims: "To create a duplicate of an associative array, use .dup, which 
works the same as for 10 arrays."
So... is it a bug or is this feature missing intentionally?
What would you recommend for concise, fast and safe surrogate?

AM

bearophile <bearophileHUGS lycos.com> writes:

Adrian Matoga:
 So... is it a bug or is this feature missing intentionally?

I have asked for a .dup for AAs something like three years ago, and probably
other people have asked for it years before. I think it will be added, but I
presume nobody has implemented it yet.


 What would you recommend for concise, fast and safe surrogate?

This is a possible version (untested):

TV[TK] dup(TK, TV)(TV[TK] aa) {
        TV[TK] result;
        foreach (k, v; aa)
            result[k] = v;
        return result;
}

Bye,
bearophile

Adrian Matoga <epi atari8.info> writes:

I also solved it with foreach but the way you wrapped it into a handy 
template makes it worth keeping for the future use. Thanks, bearophile!

dsimcha <dsimcha yahoo.com> writes:

== Quote from bearophile (bearophileHUGS lycos.com)'s article
 Adrian Matoga:
 So... is it a bug or is this feature missing intentionally?

 I have asked for a .dup for AAs something like three years ago, and probably

other people have asked for it years before. I think it will be added, but I
presume nobody has implemented it yet.
 What would you recommend for concise, fast and safe surrogate?

 This is a possible version (untested):
 TV[TK] dup(TK, TV)(TV[TK] aa) {
         TV[TK] result;
         foreach (k, v; aa)
             result[k] = v;
         return result;
 }
 Bye,
 bearophile

Of course that works, but you can probably do it more efficiently if you work
at a
lower level, inside aaA.d.  For example, in terms of unnecessary memory
allocations your function is roughly equivalent to using the following for
duplicating a regular array:

T[] dup(T)(T[] arr) {
    T[] ret;
    foreach(elem; arr) {
        ret ~= elem;
    }

    return ret;
}