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digitalmars.D.learn - Two little blog/tutorials posts.

reply Alan Knowles <alan akbhome.com> writes:
I wrote these two, they may be of some interest...


http://www.akbkhome.com/blog.php/View/114/interesting_languages__D.html
http://www.akbkhome.com/blog.php/View/115/More_on_Digitalmars_D__Simple_SVG_render_for_GnomeCanvas.html

I'm sure they are lacking in many ways, but feel free to post 
comments/corrections ;)

Regards
Alan
Feb 27 2006
next sibling parent reply Derek Parnell <derek psych.ward> writes:
On Tue, 28 Feb 2006 10:40:47 +0800, Alan Knowles wrote:


 I wrote these two, they may be of some interest...
 
 http://www.akbkhome.com/blog.php/View/114/interesting_languages__D.html
 http://www.akbkhome.com/blog.php/View/115/More_on_Digitalmars_D__Simple_SVG_render_for_GnomeCanvas.html
 
 I'm sure they are lacking in many ways, but feel free to post 
 comments/corrections ;)


The web pages don't display very well in Opera (v8.52 Build 7721). It looks
like some non-standard code is being used.

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocracy!"
28/02/2006 1:50:48 PM
Feb 27 2006
parent Alan Knowles <alan akbhome.com> writes:
Derek Parnell wrote:

 On Tue, 28 Feb 2006 10:40:47 +0800, Alan Knowles wrote:
 
 

I wrote these two, they may be of some interest...

http://www.akbkhome.com/blog.php/View/114/interesting_languages__D.html
http://www.akbkhome.com/blog.php/View/115/More_on_Digitalmars_D__Simple_SVG_render_for_GnomeCanvas.html

I'm sure they are lacking in many ways, but feel free to post 
comments/corrections ;)


 
 
 The web pages don't display very well in Opera (v8.52 Build 7721). It looks
 like some non-standard code is being used.
 


Yeah, only the top menu is a bit broken, I've never worked out (or 
bothered that much) how to fix it for IE/Opera, as they dont have free 
downloable CSS editors on linux. Feel free to send me patches to the CSS ;)

Regards
Alan
Feb 27 2006
prev sibling next sibling parent reply "Regan Heath" <regan netwin.co.nz> writes:
On Tue, 28 Feb 2006 10:40:47 +0800, Alan Knowles <alan akbhome.com> wrote:

 I wrote these two, they may be of some interest...


 http://www.akbkhome.com/blog.php/View/114/interesting_languages__D.html
 http://www.akbkhome.com/blog.php/View/115/More_on_Digitalmars_D__Simple_SVG_render_for_GnomeCanvas.html

 I'm sure they are lacking in many ways, but feel free to post  
 comments/corrections ;)


Nice work! (but like Derek mentioned it doesn't look so good in Opera)

I'm mostly sure this is incorrect however (someone else correct me if I'm  
wrong)..

"
File f = new File( r"/tmp/data.svg", FileMode.In );
while (!f.eof()) {
   testdata ~= f.readString(  f.available());
}
almost as simple as file_get_contents(), and since D cleans up the File  
handle at the end of the method it's in, you dont really need to delete f  
to close the file handle."

D is garbage collected and the collector does not guarantee to call the  
destructor for the File object. So, the above code may never close the  
file.

However, D has a feature currently called 'auto' (I say 'currently'  
because there is some debate on the topic of late)

auto File f = new File( r"/tmp/data.svg", FileMode.In );
while (!f.eof()) {
   testdata ~= f.readString(  f.available());
}

'auto' will ensure the File object is deleted at the end of the scope.

Also, a recent new feature "on scope" can help here too:
   http://www.digitalmars.com/d/exception-safe.html
   http://www.digitalmars.com/d/statement.html#scope

Oh, and std.file contains a function "read" which will read an entire file  
into an array. It returns a void[] which can be cast to whatever array  
type you actually require, eg.

import std.file;
import std.stdio;

void main()
{
	wchar[] text = cast(wchar[])read("utf16.txt");
	writefln(text);
}

Regan
Feb 27 2006
next sibling parent reply "Regan Heath" <regan netwin.co.nz> writes:
On Tue, 28 Feb 2006 16:15:38 +1300, Regan Heath <regan netwin.co.nz> wrote:

 D is garbage collected and the collector does not guarantee to call the  
 destructor for the File object. So, the above code may never close the  
 file.


Which reminds me, your other statement in the first article:

"memory management (autofreeing at the end of each function) - so you dont  
need to splatter the code with malloc)(/free()"

should probably mention the garbage collector as the reason you don't need  
malloc/free.

The statement:
   "autofreeing at the end of each function"

isn't exactly true, the current GC tends to free when resources get tight,  
i.e. you ask for more memory and there isn't enough.

Regan
Feb 27 2006
parent Alan Knowles <alan akbhome.com> writes:
Thanks, I'll have a look at updating them later, so they are more 
technically acurate

Regards
Alan

Regan Heath wrote:

 On Tue, 28 Feb 2006 16:15:38 +1300, Regan Heath <regan netwin.co.nz> wrote:
 

 D is garbage collected and the collector does not guarantee to call 
 the  destructor for the File object. So, the above code may never 
 close the  file.


 
 
 Which reminds me, your other statement in the first article:
 
 "memory management (autofreeing at the end of each function) - so you 
 dont  need to splatter the code with malloc)(/free()"
 
 should probably mention the garbage collector as the reason you don't 
 need  malloc/free.
 
 The statement:
   "autofreeing at the end of each function"
 
 isn't exactly true, the current GC tends to free when resources get 
 tight,  i.e. you ask for more memory and there isn't enough.
 
 Regan
Feb 27 2006
prev sibling parent Derek Parnell <derek psych.ward> writes:
On Tue, 28 Feb 2006 16:15:38 +1300, Regan Heath wrote:


 
 Oh, and std.file contains a function "read" which will read an entire file  
 into an array. It returns a void[] which can be cast to whatever array  
 type you actually require, eg.
 
 import std.file;
 import std.stdio;
 
 void main()
 {
 	wchar[] text = cast(wchar[])read("utf16.txt");
 	writefln(text);
 }


Just to clarify, the cast here "cast(wchar[])" does not convert the bytes
read in to UTF16. If you use a cast here, the bytes must already by in the
order implied by the cast. Thus "cast(wchar[])" is useful if the file is
already  UTF16 encoded file. If the file is, say ASCII or UTF8, and you
need it converted to UTF16, ...

    wchar[] text = std.utf.toUTF16(cast(char[])read("utf08.txt"))

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocracy!"
28/02/2006 3:23:28 PM
Feb 27 2006
prev sibling parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Alan Knowles" <alan akbhome.com> wrote in message 
news:du0d5a$5j0$1 digitaldaemon.com...

 I'm sure they are lacking in many ways, but feel free to post 
 comments/corrections ;)


Oh, you poor man!  Writing code like you're still in C!  This is D we're 
talking about here.

int main(char[][] args)
{
    writefln("Hello World");
    writefln("args.length = ", args.length);

    for (int i = 0; i < args.length; i++)
    {
        // Still a good idea to use the %s, so it doesn't escape the arg 
string
        writefln("args[", i, "] = '%s'", args[i]);
    }

    return 0;
}

Or even:

    foreach (uint i, char[] arg; args)
    {
        writefln("args[", i, "] = '%s'", arg);
    }

Also, this isn't valid code:

char[char[]] testarray =
[
    "one": "1",
    "two": "2"
];

There are no associative array initializers yet.  In fact, there are no 
non-static array initializers (dumb, I know).  They've been proposed, but 
they don't exist.
Feb 27 2006
parent reply Ivan Senji <ivan.senji_REMOVE_ _THIS__gmail.com> writes:
Jarrett Billingsley wrote:

 "Alan Knowles" <alan akbhome.com> wrote in message 
 news:du0d5a$5j0$1 digitaldaemon.com...
 

I'm sure they are lacking in many ways, but feel free to post 
comments/corrections ;)


 
 
 Oh, you poor man!  Writing code like you're still in C!  This is D we're 
 talking about here.
 
 int main(char[][] args)
 {
     writefln("Hello World");
     writefln("args.length = ", args.length);
 
     for (int i = 0; i < args.length; i++)
     {
         // Still a good idea to use the %s, so it doesn't escape the arg 
 string
         writefln("args[", i, "] = '%s'", args[i]);
     }
 
     return 0;
 }
 
 Or even:
 
     foreach (uint i, char[] arg; args)
     {
         writefln("args[", i, "] = '%s'", arg);
     }
 


Or even:

foreach(i, arg; args)
{
...
}
Feb 28 2006
parent "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Ivan Senji" <ivan.senji_REMOVE_ _THIS__gmail.com> wrote in message 
news:du1an7$16so$1 digitaldaemon.com...

 Or even:

 foreach(i, arg; args)
 {
 ...
 }


Autotyping scares me.  I like knowing exactly what everything is.
Feb 28 2006