On Thursday, 26 January 2017 at 02:29:07 UTC, Ivan Kazmenko wrote:
On Thursday, 26 January 2017 at 01:47:53 UTC, Profile Anaysis
wrote:
does this mean that have
int[][4][4] matrix_history;
backwards?
int[4][4][] matrix_history;
this creates even a more set of problems.
In short, you are right, `int[4][4][]` is a dynamic array of
`int[4][4]`. In turn, `int[4][4]` is a static length-4 array
of `int[4]`, and that is a static length-4 array of `int`.
It's quite logical once you learn how to read it: if T is a
type, then T[] is a dynamic array of that type, and T[4] is a
static length-4 array of that type.
So, if I have `int[2][5][7] a;` somewhere, the very last
element is `a[6][4][1]`. If you are inclined to think in terms
of this difference, the simple rule of thumb would be that the
order of dimensions in the declaration is reversed.
Thanks, knowing the last element is important ; Basically I just
need to know the proper index. For me, having the array declared
in symbolic form that matches the indexing, like in C/C++, is
quicker, easier to remember, and harder to forget. I don't really
care too much beyond that. They could be declared any way... but
I find myself getting confused in D because of little things like
this that don't carry over while almost everything else is.
Also, note that if you want to have, for example, a dynamic
array of 5 dynamic arrays of the same length 7 (modeling a C
rectangular array, or a D static array, but with possibility to
change the length of each row, as well as the number of rows),
you would go with
`auto a = new int [] [] (5, 7);` (initialization)
The static array of 5 static arrays of length 7 is still
`int [7] [5] a;` (type declaration)
So the reverse only happens in type declarations.
(On the contrary, declarations in C or C++ looks rather
unintuitive from this perspective: `T a[4][5][6]` is means that
`a` is an array of 4 arrays of 5 arrays of 6 arrays of `T`.
Note how we have to read left-to-right but then wrap around the
string to get the meaning.)
lol, I don' tknow what the last sentence means. wrap around the
string? Do you mean look at the variable?
For me the interpretation above is the most logical because it is
a sequential operation in my mind, if you will. x of y of z and
the chain can be cut off anywhere and the interpretation still be
the same.
Since I am a native speaker of English, which is a left to right
language, it just makes sense. I, am, of coursed biased because I
started with C/C++ rather than D.
Additionally, reading about various kinds of arrays in D might
help:
https://dlang.org/spec/arrays.html
And more in-depth material about array slicing:
http://dlang.org/d-array-article.html
Ivan Kazmenko.
