Hello, folks! Newbie to D, have some questions!

[timmyjose via Digitalmars-d-learn]

On Monday, 20 February 2017 at 15:27:16 UTC, ag0aep6g wrote:
> On 02/20/2017 03:44 PM, timmyjose wrote:
>> Things I don't like so much:
>>
>> 1). The std.range: iota function(?) is pretty nice, but the 
>> naming seems
>> a bit bizarre, but quite nice to use.
>
> Yeah, the name is weird. A little googling suggests it comes 
> from C++ [1] which took it from APL.

Damn! I'd just watched this interesting APL demo from 1975 a 
couple of days back
(https://www.youtube.com/watch?v=_DTpQ4Kk2wA) which does use 
iota, and I never did make the connection!

>> 2). The automatic conversion rules are nice for avoiding 
>> verbose code,
>> but it looks like it might bite one just like in C++.
>
> D at least disallows narrowing conversions. But yeah, 
> conversions between signed/unsigned, from integral to floating 
> point, or from narrower to wider char variants can have 
> surprising results.
>
>> 3). Not so much a fan of "auto", but it does have its uses, of 
>> course.
>
> `auto` can obscure your code, but it can also make it more DRY. 
> And with ranges and their combinations, types quickly get too 
> complex to type out.

Absolutely agreed.

>> 4). I'm still a bit confused by order of dimensions in 
>> rectangular arrays:
>>
>> Suppose I have a simple 2 x 3 array like so:
>>
>> import std.stdio;
>> import std.range: iota;
>>
>> void main() {
>>     // a 2 x 3 array
>>     int [3][2] arr;
>>
>>     foreach (i; iota(0, 2)) {
>>         foreach(j; iota(0, 3)) {
>>             arr[i][j] = i+j;
>>         }
>>     }
>>
>>     writefln("second element in first row = %s", arr[0][1]);
>>     writefln("third element in second row = %s", arr[1][2]);
>>
>>     writeln(arr);
>> }
>>
>> My confusion is this - the declaration of the array is arr
>> [last-dimension]...[first-dimension], but the usage is
>> arr[first-dimension]...[last-dimension]. Am I missing 
>> something here?
>
> You've got it. Declarations have the form `Type name;`. 
> Fixed-size array types have the form `E[n]`. E can itself be 
> another fixed-size array type, say F[m]. Then the whole type 
> becomes F[m][n]. Simple.

Brilliant! This explanation actually makes me get it now.

> The syntax could have be designed to grow in the other 
> direction: [n]E = [n][m]F, to match indexing order. But Walter 
> didn't make it that way.
>
>
> [1] http://en.cppreference.com/w/cpp/algorithm/iota