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digitalmars.D.learn - Basic Syntax Question

reply "WhatMeWorry" <kc_heaser yahoo.com> writes:
I don't suppose there is a digital.D.beginner forum?

I've been staring at this definition for about an hour and I 
still can't decode it.

int[string][double[int[]]] a;  //
...
auto b = to!(short[wstring][string[double[]]])(a);  // this 
doesn't help either


int[string} a  // would be an Associate Array of integers with a 
string key?

int[]  // would be a dynamic array of integers,i believe?

But put the int[] inside of double[] and put that inside of [] 
and put that after the associative array, and my head can't stop 
for spinning.


If there is a better site or forum, please tell me and I won't 
waste people's time here. I did buy Andrei Alexandrescu's book 
and have it pretty well dog-eared. But i must be a pretty 
mediocre programmer.
Apr 02 2013
next sibling parent reply "Tobias Pankrath" <tobias pankrath.net> writes:
On Tuesday, 2 April 2013 at 16:24:46 UTC, WhatMeWorry wrote:

 I don't suppose there is a digital.D.beginner forum?


There is D.learn. Scroll down in the webinterface :-)


 I've been staring at this definition for about an hour and I 
 still can't decode it.

 int[string][double[int[]]] a;  //


Read it left to right :-)

Let's rewrite the type with placeholders U,V.
int[string][double[int[]]] --> int[U][V]

int[U][V] is an AA mapping keys of type V to values int[U], which 
is itself an AA that maps U's to int's.

Now, what is U and V? U is string that was easy. V is 
double[int[]]. That again is an AA, mapping from int[] to double.



 int[string} a  // would be an Associate Array of integers with 
 a string key?


Nope, thats in syntax error.


 int[]  // would be a dynamic array of integers,i believe?


Correct.
Apr 02 2013
parent "John Colvin" <john.loughran.colvin gmail.com> writes:
On Tuesday, 2 April 2013 at 16:51:45 UTC, Tobias Pankrath wrote:

 On Tuesday, 2 April 2013 at 16:24:46 UTC, WhatMeWorry wrote:

 I don't suppose there is a digital.D.beginner forum?


 There is D.learn. Scroll down in the webinterface :-)


This is in D.learn already.


 int[string} a  // would be an Associate Array of integers with 
 a string key?


 Nope, thats in syntax error.


Just a } vs ]  typo (just to avoid confusion)
Apr 02 2013
prev sibling next sibling parent reply "John Colvin" <john.loughran.colvin gmail.com> writes:
On Tuesday, 2 April 2013 at 16:24:46 UTC, WhatMeWorry wrote:

 I don't suppose there is a digital.D.beginner forum?

 I've been staring at this definition for about an hour and I 
 still can't decode it.

 int[string][double[int[]]] a;  //
 ...
 auto b = to!(short[wstring][string[double[]]])(a);  // this 
 doesn't help either


 int[string} a  // would be an Associate Array of integers with 
 a string key?

 int[]  // would be a dynamic array of integers,i believe?

 But put the int[] inside of double[] and put that inside of [] 
 and put that after the associative array, and my head can't 
 stop for spinning.


 If there is a better site or forum, please tell me and I won't 
 waste people's time here. I did buy Andrei Alexandrescu's book 
 and have it pretty well dog-eared. But i must be a pretty 
 mediocre programmer.


I'm confused, did you find that definition somewhere or did you 
write it yourself?

int[string][double[int[]]]

Let's split it up:
alias double[int[]] T;

T is an associative array with key type int[] and value type 
double

So we now have
int[string][T]
Which is an associative array with key type T and value type 
int[string] (itself an associative array)

I hope that makes more sense.
Apr 02 2013
parent "WhatMeWorry" <kc_heaser yahoo.com> writes:
On Tuesday, 2 April 2013 at 16:52:17 UTC, John Colvin wrote:

int[string][double[int[]]] a;


 I'm confused, did you find that definition somewhere or did you 
 write it yourself?


I found the above in an example in std.conv; Thank you, but I can 
assure you my brain is not powerful enough to come up with such a 
construct.
Apr 02 2013
prev sibling parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 04/02/2013 09:24 AM, WhatMeWorry wrote:>

 I don't suppose there is a digital.D.beginner forum?

 I've been staring at this definition for about an hour and I still can't
 decode it.

 int[string][double[int[]]] a;  //


alias usually makes the syntax cleaner but that is still pretty crazy. :)

void main()
{
     int[string][double[int[]]] a;

     alias Numbers = int[];
     alias NumbersToDoubleDict = double[Numbers];
     alias StringToIntDict = int[string];
     alias CrazyDict = StringToIntDict[NumbersToDoubleDict];

     CrazyDict b;

     static assert(is(typeof(a) == typeof(b)));
}

Ali
Apr 02 2013