Hey...

Compiler is now working as expected! Thank's to a great catch by Michel Fortin!

A little further down the tutorial "D_ A Newbie-Oriented Tutorial", there's this code:

[code]
import std.stdio;

void main()
{
	int[] intArray;

  intArray[0] = 42;
  intArray[1] = 54;
  intArray[2] = 91;

  writefln("The lemgth of the intArray is %d.",
         intArray.length);
}
[/code]

It compiles with no error or warning - AFAICT. However, it chokes upon execution with:

dnormandin@ ~/programming/dmd2/code
01:40 pm >> arrays_in_d
core.exception.RangeError@arrays_in_d(7): Range violation

I've read and re-read the tutorial content, but it's not jumping out at me.
-- 
duke

Duke Normandin wrote:
> Hey...
> 
> Compiler is now working as expected! Thank's to a great catch by
> Michel Fortin!
> 
> A little further down the tutorial "D_ A Newbie-Oriented Tutorial",
> there's this code:
> 
> [code]
> import std.stdio;
> 
> void main()
> {
> 	int[] intArray;
> 
>   intArray[0] = 42;
>   intArray[1] = 54;
>   intArray[2] = 91;
> 
>   writefln("The lemgth of the intArray is %d.",
>          intArray.length);
> }
> [/code]
> 
> It compiles with no error or warning - AFAICT. However, it chokes
> upon execution with:
> 
> dnormandin@ ~/programming/dmd2/code
> 01:40 pm >> arrays_in_d
> core.exception.RangeError@arrays_in_d(7): Range violation
> 
> I've read and re-read the tutorial content, but it's not jumping out
> at me.

The array initially has length of zero.
You need to write something like:
intArray = new int[3];
or
intArray.length = 3;
before putting anything into it.

Don:
> The array initially has length of zero.
> You need to write something like:
> intArray = new int[3];
> or
> intArray.length = 3;
> before putting anything into it.

In some languages (Perl? Maybe Lua and PHP) arrays auto-create empty slots as needed, but in many languages you need to tell the language that you want some empty slots before you can put values inside them (this stricter behaviour can probably catch some bugs, and allows to produce faster programs).

Another way to add items to a D dynamic array like intArray is to append them at the end, the language runtime takes care of creating new slots as needed:

int[] intArray;
intArray ~= 1;
intArray ~= 2;
intArray ~= 3;

Bye,
bearophile

On Fri, 28 May 2010, bearophile wrote:

> Don:
> > The array initially has length of zero.
> > You need to write something like:
> > intArray = new int[3];
> > or
> > intArray.length = 3;
> > before putting anything into it.
>
> In some languages (Perl? Maybe Lua and PHP) arrays auto-create empty slots as needed, but in many languages you need to tell the language that you want some empty slots before you can put values inside them (this stricter behaviour can probably catch some bugs, and allows to produce faster programs).
>
> Another way to add items to a D dynamic array like intArray is to append them at the end, the language runtime takes care of creating new slots as needed:
>
> int[] intArray;
> intArray ~= 1;
> intArray ~= 2;
> intArray ~= 3;
>
> Bye,
> bearophile


@Don
@bearophile

Would you guys visit this URL real quick

http://compsci.ca/v3/viewtopic.php?t=9518

This is the site that I'm using to learn D. If you scroll down 3-4 screens full, you'll come to the "array" topic. Is this tutorial outdated, wrong, or what, because it doesn't deem to sync with what you two fine fellows are telling me about creating dynamic arrays in the D-Language. TIA..
-- 
duke

Duke Normandin:

> This is the site that I'm using to learn D. If you scroll down 3-4 screens full, you'll come to the "array" topic. Is this tutorial outdated, wrong, or what, because it doesn't deem to sync with what you two fine fellows are telling me about creating dynamic arrays in the D-Language. TIA..

That part of that tutorial is not outdated, as far as I know it's just wrong. You can auto-create slots in associative arrays:

int[int] aa;
aa[0] = 1;
aa[1] = 1;
aa[2] = 1;

Lua language uses associative arrays instead of arrays :-)

Bye,
bearophile

On Fri, 28 May 2010, bearophile wrote:

> Duke Normandin:
>
> > This is the site that I'm using to learn D. If you scroll down 3-4 screens full, you'll come to the "array" topic. Is this tutorial outdated, wrong, or what, because it doesn't deem to sync with what you two fine fellows are telling me about creating dynamic arrays in the D-Language. TIA..
>
> That part of that tutorial is not outdated, as far as I know it's just wrong. You can auto-create slots in associative arrays:
>
> int[int] aa;
> aa[0] = 1;
> aa[1] = 1;
> aa[2] = 1;
>
> Lua language uses associative arrays instead of arrays :-)
>
> Bye,
> bearophile
>


So these two paragraphs in the tutorial are flat out wrong?

[quote]
You should note that I never specified how long the array should be.
Instead I simply assigned values to various positions in the array and
it just worked.
This is an example of a dynamic array. It will grow to whatever size
is required. I can determine the size of an array at any time by
accessing the array's length property. The length property can also
have a value assigned to it to resize the array.
[/quote]

Maybe the link for this tutorial at:

http://www.prowiki.org/wiki4d/wiki.cgi?FirstLanguage

should be removed?

-- 
duke

Duke Normandin <dukeofperl@ml1.net> wrote:

> So these two paragraphs in the tutorial are flat out wrong?

Absolutely.

-- 
Simen

On Sat, 29 May 2010, Simen kjaeraas wrote:

> Duke Normandin <dukeofperl@ml1.net> wrote:
>
> > So these two paragraphs in the tutorial are flat out wrong?
>
> Absolutely.

Then I'm done with _that_ site - can't trust it!

Any chance that you could suggest a good beginner's D tutorial?

-- 
duke

Hello Simen,

> Duke Normandin <dukeofperl@ml1.net> wrote:
> 
>> So these two paragraphs in the tutorial are flat out wrong?
>> 
> Absolutely.
> 

Any idea who owns it so it can get changed? For that matter, who added the link?

Being paranoid for the moment (it can be fun sometimes :) that blurb is so wrong that I wonder if it's an attempt to frustrate newbies away from D?

-- 
... <IXOYE><

On Fri, 28 May 2010 22:42:32 -0400, Duke Normandin <dukeofperl@ml1.net> wrote:

> On Sat, 29 May 2010, Simen kjaeraas wrote:
>
>> Duke Normandin <dukeofperl@ml1.net> wrote:
>>
>> > So these two paragraphs in the tutorial are flat out wrong?
>>
>> Absolutely.
>
> Then I'm done with _that_ site - can't trust it!
>
> Any chance that you could suggest a good beginner's D tutorial?
>

It's quite possible that the example code *worked* at some very early version of the D compiler.

Nowadays, all arrays are initialized with null as the pointer, guaranteeing that the first time you access array[0], it will segfault.  So with the current compilers, that code is *guaranteed* to not work.

I speak not from experience, ever since I've started using D it always initializes arrays to null.  I just can't imagine that someone would have written such a tutorial without having some experience with D, and without ever having compiled the code.  So my logical conclusion is that either 1) at some point, that code did work, 2) the author was so convinced of his D mastery that he didn't bother to try any of his examples, or 3) the page is a blatant attempt to make users not like D.

I find 2 unlikely since he specifically mentions how you don't have to initialize arrays.

I wonder if someone recalls the feature set of the dmd compiler from July, 2005.

-Steve