Best ways to declare associative arrays

[Nicholas Wilson via Digitalmars-d-learn]

On Sunday, 12 March 2017 at 07:58:40 UTC, helxi wrote:
> How would an experienced programmer declare an associative 
> array of strings that has 2 keys?
>
> My initial impression was string[string][2] my_array; which 
> does not seem to work.
>
> Here is a snippet of the code I am working on:
>
>
> import std.string;
> import std.stdio;
>
>
> string[string] change(ref string[string] arg_array){
> 	//..
> 	arg_array["first"] = strip(readln());
> 	//..
> 	arg_array["second"] = strip(readln());
> 	//..
> 	return def;
> }
>

You appear to be confused about the way arrays work.
string[string] foo; //declares an assoc array of strings, index 
by string
string[string][2] bar; // declares a static array of two 
string[string]
foo = { "key1" : "some data", "key2" :  "some other data" }; // 
initialise foo with some data
foo["blarg"] = "fxgsdzfcxf"; // insert some more data

> associative array of strings that has 2 keys?

is a regular associative array that has two entries. much like 
the difference between
int[] baz = [1 ,2]; // has two elements
int[][2] quux; // a static array of length 2 whose elements are 
of type int[]

> void main(){
> 	string[string][2] test; // remove the `[2]`
> 	change(string[string] test);
just do
         change(test);
it is invalid syntax to have a type before the variable in a 
function call, unless you were trying to cast it, in which use 
`cast(type)(expression)`
> }
> 	

If you wish to reserve capacity for the array, use 
`arr.reserve(N)` to allocate memory enough to hold N elements.