www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Read integer from console and sleep

reply "Iain" <staffell gmail.com> writes:
I tried to use the sleep function from the Rosetta Code project: 
http://rosettacode.org/wiki/Sleep#D

Am I right in thinking this is D1 code, as it will not compile 
under 2.059?

So, I tried writing my own version, and hit my head against many 
brick walls along the way.  My result takes more lines than C, 


Could anyone explain how to optimise the code below before I post 
it to Rosetta?

-----------------
import std.stdio;
import std.conv;
import std.string;
import core.thread;

void main()
{
   write("Enter a time to sleep (in seconds): ");
   string input = stdin.readln(); // have to make this a string 
first, it can't go directly into parse!
   auto time = parse!long(input); // have to use parse!, as to! 
crashes when it sees a \n
   writeln("Sleeping...");
   Thread.sleep( dur!("seconds")(time) );
   writeln("Awake!");
}


Many thanks!
May 04 2012
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 05/04/2012 06:18 AM, Iain wrote:

 I tried to use the sleep function from the Rosetta Code project:
 http://rosettacode.org/wiki/Sleep#D

 Am I right in thinking this is D1 code, as it will not compile under 


2.059?

 So, I tried writing my own version, and hit my head against many brick

 I'm guessing it can't be the best solution.

 Could anyone explain how to optimise the code below before I post it to
 Rosetta?

 -----------------
 import std.stdio;
 import std.conv;
 import std.string;
 import core.thread;

 void main()
 {
 write("Enter a time to sleep (in seconds): ");
 string input = stdin.readln(); // have to make this a string first, it
 can't go directly into parse!
 auto time = parse!long(input); // have to use parse!, as to! crashes
 when it sees a \n
 writeln("Sleeping...");
 Thread.sleep( dur!("seconds")(time) );
 writeln("Awake!");
 }


 Many thanks!


You can use spaces in the format string to read and ignore all 
whitespace. This one ignores the '\n' and others that may have been left 
over from the previous read (I know that there can't be any in this 
small program):

import std.stdio;
import core.thread;

void main()
{
   write("Enter a time to sleep (in seconds): ");

   long time;
   readf(" %s", &time);

   writeln("Sleeping...");
   Thread.sleep( dur!("seconds")(time) );
   writeln("Awake!");
}

Some people have developed their own input modules. Reading any type can 
be as simple as in the following:

import std.stdio;
import core.thread;

T read(T)(string prompt)
{
     T value;
     write(prompt);
     readf(" %s", &value);
     return value;
}

void main()
{
   immutable time =
       read!long("Enter a time to sleep (in seconds): ");

   writeln("Sleeping...");
   Thread.sleep(dur!("seconds")(time));
   writeln("Awake!");
}

Ali
May 04 2012
parent reply "bearophile" <bearophileHUGS lycos.com> writes:
Ali Çehreli:


 import std.stdio;
 import core.thread;

 void main()
 {
   write("Enter a time to sleep (in seconds): ");

   long time;
   readf(" %s", &time);

   writeln("Sleeping...");
   Thread.sleep( dur!("seconds")(time) );
   writeln("Awake!");
 }


If you want Iain I'll put this version by Ali Çehreli in 
Rosettacode:

import std.stdio, core.thread;

void main() {
     write("Enter a time to sleep (in seconds): ");

     long secs;
     readf(" %d", &secs);

     writeln("Sleeping...");
     Thread.sleep(dur!"seconds"(secs));
     writeln("Awake!");
}


Bye,
bearophile
May 04 2012
parent reply "Iain" <staffell gmail.com> writes:
 If you want Iain I'll put this version by Ali Çehreli in 
 Rosettacode:

 import std.stdio, core.thread;

 void main() {
     write("Enter a time to sleep (in seconds): ");

     long secs;
     readf(" %d", &secs);

     writeln("Sleeping...");
     Thread.sleep(dur!"seconds"(secs));
     writeln("Awake!");
 }


 Bye,
 bearophile


That's great, and thanks to Ali for explaining.

Out of interest, is there a coordinated effort to update things 
like Rosetta or the dsource.org tutorials to use D2.0?  I find 
one of the big stumbling blocks to learning is that half of the 
tutorials and code snippets out there are obsolete!
May 04 2012
next sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 05/04/2012 10:51 AM, Iain wrote:

 If you want Iain I'll put this version by Ali Çehreli in Rosettacode:

 import std.stdio, core.thread;

 void main() {
 write("Enter a time to sleep (in seconds): ");

 long secs;
 readf(" %d", &secs);

 writeln("Sleeping...");
 Thread.sleep(dur!"seconds"(secs));
 writeln("Awake!");
 }


 Bye,
 bearophile


 That's great, and thanks to Ali for explaining.

 Out of interest, is there a coordinated effort to update things like
 Rosetta or the dsource.org tutorials to use D2.0? I find one of the big
 stumbling blocks to learning is that half of the tutorials and code
 snippets out there are obsolete!


As far as I know, people maintain sites individually.

It is unfortunate but not surprising that many sites have been outdated 
considering the amount of changes to D in the recent years. I had to 
rewrite a number of chapters and go over many examples since I have 
started the original book a number of years ago. (See my shiny new 
signature. ;))

Somewhat off-topic, I have just hit a broken example today when 
translating the "null and is" chapter. This used to print 0:

     writeln(null);

but now causes an obscure compilation error:

.../dmd/phobos/std/stdio.d(1562): Error: undefined identifier 'length'
.../dmd/phobos/std/stdio.d(1562): Error: undefined identifier 'ptr', did 
you mean 'template tr(C1,C2,C3,C4 = immutable(char))'?
deneme.d(76953): Error: template instance 
std.stdio.writeln!(typeof(null)) error instantiating

It takes the 'null' value to be a "Specialization for strings - a very 
frequent case".

This is a bug, right? But what should printing 'null' do anyway? Print 0 
as before, or "null"?

Ali

-- 
D Programming Language Tutorial: http://ddili.org/ders/d.en/index.html
May 04 2012
parent "bearophile" <bearophileHUGS lycos.com> writes:
Ali Çehreli:


 This is a bug, right? But what should printing 'null' do 
 anyway? Print 0 as before, or "null"?


http://d.puremagic.com/issues/show_bug.cgi?id=8040

Bye,
bearophile
May 04 2012
prev sibling parent reply "bearophile" <bearophileHUGS lycos.com> writes:
Iain:


 Out of interest, is there a coordinated effort to update things 
 like Rosetta or the dsource.org tutorials to use D2.0?


In the last weeks I have rewritten/fixed/updated more than 480 D 
entries (some Rosettacode Tasks have more than one D 
implementation). But there are about 110 entries left to update.

Bye,
bearophile
May 04 2012
parent "Iain" <staffell gmail.com> writes:
On Friday, 4 May 2012 at 19:37:40 UTC, bearophile wrote:

 Iain:


 Out of interest, is there a coordinated effort to update 
 things like Rosetta or the dsource.org tutorials to use D2.0?


 In the last weeks I have rewritten/fixed/updated more than 480 
 D entries (some Rosettacode Tasks have more than one D 
 implementation). But there are about 110 entries left to update.

 Bye,
 bearophile


Wow!  It's people like you who are making D understandable for 
the rest of us.  Thank you!

As a testament to my learning, I have updated 
http://rosettacode.org/wiki/User_input/Text#D
May 09 2012