Simplest way to create an array from an associative array which its contains keys and values?
Craig Dillabaugh
cdillaba at cg.scs.carleton.ca
Tue Jan 7 13:21:19 PST 2014
On Tuesday, 7 January 2014 at 20:52:40 UTC, H. S. Teoh wrote:
> On Tue, Jan 07, 2014 at 08:38:10PM +0000, Craig Dillabaugh
> wrote:
> [...]
>> As someone with little experience with functional programming,
>> I am
>> just curious - having browsed through the thread - if the
>> various
>> solutions proposed here would really be considered more
>> 'idiomatic'
>> D. Or if they were posted because the OP asked about avoiding
>> the
>> foreach() loop.
>>
>> In other words while:
>>
>> auto range = aa.byKey.map!(a => chain(a.only, aa[a].only));
>> string[] array = range.join;
>>
>> Saves a few lines of code, and looks cooler, it seems that the
>> trivial foreach loop version is very easy:
>>
>> string[] array;
>>
>> foreach (key, value; aa) {
>> array ~= key;
>> array ~= value;
>> }
> [...]
>
> Even better, encapsulate this in a function:
>
> CommonType!(K,V)[] aaToArray(K,V)(V[K] aa)
> if (is(CommonType!(V, K)))
> {
> typeof(return) result;
> foreach (key, value; aa) {
> result ~= key;
> result ~= value;
> }
> return result;
> }
>
> Then you can use it in a single line next time:
>
> string[] arr = aaToArray(["a": "aa", "b" : "bb"]);
> int[] arr = aaToArray([1: 2, 3: 4]);
> ... // etc.
>
>
> T
Yes, I would imagine if this was not a 'one off' operation, you
would likely want to create a function. That one looks nice.
I posted my question mainly because D advertises itself as a
'multi-paradigm' language. It seems that a number of the more
experienced posters on here seem to like functional approaches
using the algorithms in std.algorithm.
However, it seems to me sometimes the obvious/simple solution
that avoids using std.algorithm results in more readable code. So
I was curious to know if using std.algorithm functions are
generally considered preferable for simple cases like this, or if
it is simply a matter of taste.
As an aside, the trade-off is even more blatant in C++ where a
simple hand-rolled solution often comes out looking so much nicer
than the STL <algorithm> alternative.
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