www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Yes or No Options

reply "Alex" <age bcc-group.de> writes:
Hey guys!

I am super new to programming and still trying to learn the very 
basics via a book that I bought.

My problem is the following:



import std.stdio;
import std.string;


void main()
{
	char[] yesno;

	write("Roll the dice: Enter a number!");
	int dieNumber;
	readf(" %s", &dieNumber);

	if (dieNumber < 4) {
	writeln("You won!");
	}
	else if ((dieNumber >= 4) && (dieNumber <= 6)) {
		writeln("I won!");
	}
	else if (dieNumber > 6){
		writeln("ERROR: Invalid Value");
	}

	writeln("Do you want to play again? Y/N?");
	readln(yesno);
	if (yesno == "Y") {
		writeln("Let's go again!");
	}

}


The program quits after "writeln("Do you want to play again? 
Y/N?");"
It ignores readln.

Furthermore: What I am actually trying to do is: If I type "Y", 
the programm should just rerun from the beginning.

I am really new to programming and there is probably a much 
easier way but this is all I know to this point.

Thanks in advance!
Jul 27 2015
next sibling parent reply "Adam D. Ruppe" <destructionator gmail.com> writes:
On Monday, 27 July 2015 at 15:50:11 UTC, Alex wrote:

 	readf(" %s", &dieNumber);


What happens here is a bit tricky and trips up a lot of 
programmers: readf leaves the end-of-line character in the 
buffer, which readln then sees as meaning its job is done.

When you enter, say, 5, then press enter, the input looks like: 
"5\n". (\n represents the newline aka end-of-line character). 
readf " %s" first skips any spaces. There's none, so it doesn't 
matter.

Then it reads in a number. So it takes the 5, leaving the rest of 
the input behind.... so that \n from pressing enter is still 
there.


readln reads everything it can until it hits a \n, picking up 
where readf left off. So the result is it immediately sees the \n 
that readf stopped on and it also stops.

An easy fix is to stick an extra readln() after the readf:

         readf(" %s", &dieNumber);
         readln(); // tell it to skip the rest of the line
         // the rest of your code is unchanged




The next thing you'll have to face is actually going again when 
they enter Y. (BTW be aware that this is case sensitive and 
readln leaves the newline at the end of the input too! So 
entering "y" won't work. And when you enter "Y"... the program 
will see "Y\n", so it won't match "let's go again" either.)

But to actually go again, you'll probably want to read about 
loops. I'll let you play with it a little from here though.
Jul 27 2015
parent reply "Alex" <age bcc-group.de> writes:
Thank you! That helped me a lot.

I'm sure that - in order to get to the point to repeat the whole 
first part of the program - I'll have to read further in the 
instructions I have BUT let's just say that I don't want it to 
repeat the first part of the program but just writeln something 
like "Ok let's do it again!" if I enter Y and press enter.

I now got to the point where the program doesn't quit but if I 
enter "Y" and hit Enter, nothing happens.

I do understand how to define an int and then compare it to a 
number I entered and do something if the number was 
smaller/bigger/the same etc.

But how do I get the programm to simply write a line if I enter a 
letter like Y?

With the code I got here it does not work. What is wrong with 
this part here:

	writeln("Do you want to play again? Y/N?");
	readf(" %s", &yesno);
	readln();
	if (yesno == "Y") {
		writeln("Yeah!");
	}


Doesn't the code mean: Write "Do you want to play again? Y/N?". 
Read keyboard input and define "yesno" by what was entered. And 
then: If what was entered was a "Y", write the following line 
"Yeah!".

Where is my error in thinking?

Sorry guys, I know it's probably something very easy..
Jul 27 2015
parent reply "Alex" <age bcc-group.de> writes:
Okay. By pure trying I found out what I did wrong:

Apparently by typing Y I entered the shift key. Could that have 
been the problem?
I changed it to a small y and it at least jumped back to the 
commandline instead of just being stuck.

And by changing:

writeln("Do you want to play again? Y/N?");
	readln(yesno);
	if (yesno == "y") {
		writeln("Yeah!");
	}

to:

writeln("Do you want to play again? Y/N?");
	readln(yesno);
	if (yesno != "y") {
		writeln("Yeah!");
	}

So instead of ==   I used  !=

Now it works. But I still do not know why..
Jul 27 2015
next sibling parent reply "Anonymous" <anon nomail.com> writes:
On Monday, 27 July 2015 at 16:48:00 UTC, Alex wrote:

 Okay. By pure trying I found out what I did wrong:

 Apparently by typing Y I entered the shift key. Could that have 
 been the problem?
 I changed it to a small y and it at least jumped back to the 
 commandline instead of just being stuck.

 And by changing:

 writeln("Do you want to play again? Y/N?");
 	readln(yesno);
 	if (yesno == "y") {
 		writeln("Yeah!");
 	}

 to:

 writeln("Do you want to play again? Y/N?");
 	readln(yesno);
 	if (yesno != "y") {
 		writeln("Yeah!");
 	}

 So instead of ==   I used  !=

 Now it works. But I still do not know why..


Check out what is the length of yesno after you do your readln.

Ex. writeln(yesno.length)

std.string.chomp may help.
Jul 27 2015
parent "CraigDillabaugh" <craig.dillabaugh gmail.com> writes:
On Monday, 27 July 2015 at 17:21:33 UTC, Anonymous wrote:

 On Monday, 27 July 2015 at 16:48:00 UTC, Alex wrote:

 Okay. By pure trying I found out what I did wrong:

 Apparently by typing Y I entered the shift key. Could that 
 have been the problem?
 I changed it to a small y and it at least jumped back to the 
 commandline instead of just being stuck.

 And by changing:

 writeln("Do you want to play again? Y/N?");
 	readln(yesno);
 	if (yesno == "y") {
 		writeln("Yeah!");
 	}

 to:

 writeln("Do you want to play again? Y/N?");
 	readln(yesno);
 	if (yesno != "y") {
 		writeln("Yeah!");
 	}

 So instead of ==   I used  !=

 Now it works. But I still do not know why..


 Check out what is the length of yesno after you do your readln.

 Ex. writeln(yesno.length)

 std.string.chomp may help.


Also, notice in Namespace's answer above the use of:

  if (yesno.toLower() != "y")

This ensures that whether the user typed 'Y' or 'y' then check 
works properly.  Which is likely what the user expects.

The 'Shift' key does not add any new symbols to the string (it 
only modifies what symbols are added).
Jul 27 2015
prev sibling parent reply "Tofu Ninja" <emmons0 purdue.edu> writes:
On Monday, 27 July 2015 at 16:48:00 UTC, Alex wrote:

 Okay. By pure trying I found out what I did wrong:

 Apparently by typing Y I entered the shift key. Could that have 
 been the problem?
 I changed it to a small y and it at least jumped back to the 
 commandline instead of just being stuck.

 And by changing:

 writeln("Do you want to play again? Y/N?");
 	readln(yesno);
 	if (yesno == "y") {
 		writeln("Yeah!");
 	}

 to:

 writeln("Do you want to play again? Y/N?");
 	readln(yesno);
 	if (yesno != "y") {
 		writeln("Yeah!");
 	}

 So instead of ==   I used  !=

 Now it works. But I still do not know why..


readln includes the '\n' at the end, so when you typed "Y" and 
pressed enter, readln returned "Y\n" which != "Y".
Jul 27 2015
parent "Alex" <age bcc-group.de> writes:
So I now combined a few of the options here and got this, which 
finally works:

import std.stdio;
import std.string;
import std.random;

void main()
{
	while (true) {
	string yesno;
	int weiter;
	char[] uschi;
	
	write("Press ENTER to roll the dice!");
	readln(uschi);
	if (uschi == "\n") {
	auto rng = uniform(1, 6);
	writeln(rng);
	
	if (rng < 4) {
		writeln("You won!");
	}
	else if ((rng >= 4) && (rng <= 6)) {
		writeln("I won!");
	}
	else if (rng > 6){
		writeln("ERROR: Invalid Value");
	}
	
	writeln("Do you want to play again? Y/N?");
	yesno = readln();
	if (yesno.toLower() != "y\n") {
		writeln("Damn it");
				break;
	}
     }
	}
}




Thank you ! :)
Jul 28 2015
prev sibling next sibling parent "Namespace" <rswhite4 gmail.com> writes:
Look at my example:
----
import std.stdio;
import std.string;
import std.conv : to;

void main()
{
     while (true) {
         write("Roll the dice: Enter a number: ");
         int dieNumber = readln.strip.to!int;

         if (dieNumber < 4) {
             writeln("You won!");
         }
         else if ((dieNumber >= 4) && (dieNumber <= 6)) {
             writeln("I won!");
         }
         else if (dieNumber > 6){
             writeln("ERROR: Invalid Value");
         }

         writeln("Do you want to play again? Y/N?");
         immutable string yesno = readln.strip;

         if (yesno.toLower() != "y")
             break;

         writeln("Let's go again!");
     }
}
----

With the while loop you really can "go again" ;)
Jul 27 2015
prev sibling next sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 07/27/2015 08:50 AM, Alex wrote:


 a book that I bought


The program looks a lot like one of the exercises in this chapter:

   http://ddili.org/ders/d.en/if.html

You didn't actually pay for it, right? Because it is free. :)

Ali
Jul 27 2015
parent reply "Alex" <age bcc-group.de> writes:
On Monday, 27 July 2015 at 17:31:08 UTC, Ali Çehreli wrote:

 On 07/27/2015 08:50 AM, Alex wrote:


 a book that I bought


 The program looks a lot like one of the exercises in this 
 chapter:

   http://ddili.org/ders/d.en/if.html

 You didn't actually pay for it, right? Because it is free. :)

 Ali




Yes! I am really sorry. I did not buy it. Thanks for this book, 
it is really cool to learn and understandable even for people 
like me that have never had any contact with programming!
Jul 27 2015
parent "wobbles" <grogan.colin gmail.com> writes:
On Monday, 27 July 2015 at 18:23:57 UTC, Alex wrote:

 On Monday, 27 July 2015 at 17:31:08 UTC, Ali Çehreli wrote:

 On 07/27/2015 08:50 AM, Alex wrote:


 a book that I bought


 The program looks a lot like one of the exercises in this 
 chapter:

   http://ddili.org/ders/d.en/if.html

 You didn't actually pay for it, right? Because it is free. :)

 Ali




 Yes! I am really sorry. I did not buy it. Thanks for this book, 
 it is really cool to learn and understandable even for people 
 like me that have never had any contact with programming!


Good on you to pick it up and learn. It's a very interesting 
field once you get past the initial learning curve!

Be sure to continue to ask questions here, I find most people 
here are very willing to help newbies :)
Jul 28 2015
prev sibling parent reply "Chris" <wendlec tcd.ie> writes:
On Monday, 27 July 2015 at 15:50:11 UTC, Alex wrote:

 Hey guys!

 I am super new to programming and still trying to learn the 
 very basics via a book that I bought.


Out of interest: what made you start with D? It's not the most 
obvious choice for a programming novice.
Jul 29 2015
parent reply "Alex" <age bcc-group.de> writes:
My father owns a small software company, specialized in market 
data products.

www.bccgi.com (in case anyone is interested)

So programming was basically around all my life.

I do a small job in his company and my next task was to learn D. 
There are two trainees and the three of us have to learn D. Ofc 
the two trainees have to learn other languages as well.

My dad said the reason why we learn this language is that he 
personally finds it to be a very intuitive language that produces 
machine code. If he just wanted us to teach programming he said 

In addition to that he wants to keep up and always have new 
languages and features in the company (only 8 people). And since 
we have experts for almost any language here but not a single one 
for D, it was time for someone to start!

Once I started I found it to be really interesting and 
challenging plus I like solving problems.


Thank you for being so nice! I have seen very few communities 
where beginners are welcomed so well!
Jul 30 2015
parent reply "Chris" <wendlec tcd.ie> writes:
On Thursday, 30 July 2015 at 14:20:41 UTC, Alex wrote:

 My father owns a small software company, specialized in market 
 data products.

 www.bccgi.com (in case anyone is interested)

 So programming was basically around all my life.

 I do a small job in his company and my next task was to learn 
 D. There are two trainees and the three of us have to learn D. 
 Ofc the two trainees have to learn other languages as well.

 My dad said the reason why we learn this language is that he 
 personally finds it to be a very intuitive language that 
 produces machine code. If he just wanted us to teach 

 In addition to that he wants to keep up and always have new 
 languages and features in the company (only 8 people). And 
 since we have experts for almost any language here but not a 
 single one for D, it was time for someone to start!

 Once I started I found it to be really interesting and 
 challenging plus I like solving problems.


 Thank you for being so nice! I have seen very few communities 
 where beginners are welcomed so well!


Very interesting indeed! Care to write an article about it one 
day? "Learning D as an absolute beginner" or something like that. 
I wonder, is your father's company listed among those using D? I 
think there's a list somewhere on Wiki, if not we should have one 
:-)
Jul 30 2015
next sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 07/30/2015 08:14 AM, Chris wrote:


 I wonder,
 is your father's company listed among those using D? I think there's a
 list somewhere on Wiki, if not we should have one :-)


I don't think they use D yet but the page is here:

   http://wiki.dlang.org/Current_D_Use

Ali
Jul 30 2015
parent "Chris" <wendlec tcd.ie> writes:
On Thursday, 30 July 2015 at 17:48:51 UTC, Ali Çehreli wrote:

 On 07/30/2015 08:14 AM, Chris wrote:


 I wonder,
 is your father's company listed among those using D? I think 
 there's a
 list somewhere on Wiki, if not we should have one :-)


 I don't think they use D yet but the page is here:

   http://wiki.dlang.org/Current_D_Use

 Ali


That's the link. Thanks! I find the reasons Alex gave for using D 
very interesting. It's beyond all hype and reddit and stuff like 
that. It shows that D attracts users for what it is, without any 
hype or sh*t like that.
Jul 31 2015
prev sibling parent "Alex" <age bcc-group.de> writes:
On Thursday, 30 July 2015 at 15:14:28 UTC, Chris wrote:

 On Thursday, 30 July 2015 at 14:20:41 UTC, Alex wrote:

 My father owns a small software company, specialized in market 
 data products.

 www.bccgi.com (in case anyone is interested)

 So programming was basically around all my life.

 I do a small job in his company and my next task was to learn 
 D. There are two trainees and the three of us have to learn D. 
 Ofc the two trainees have to learn other languages as well.

 My dad said the reason why we learn this language is that he 
 personally finds it to be a very intuitive language that 
 produces machine code. If he just wanted us to teach 

 In addition to that he wants to keep up and always have new 
 languages and features in the company (only 8 people). And 
 since we have experts for almost any language here but not a 
 single one for D, it was time for someone to start!

 Once I started I found it to be really interesting and 
 challenging plus I like solving problems.


 Thank you for being so nice! I have seen very few communities 
 where beginners are welcomed so well!


 Very interesting indeed! Care to write an article about it one 
 day? "Learning D as an absolute beginner" or something like 
 that. I wonder, is your father's company listed among those 
 using D? I think there's a list somewhere on Wiki, if not we 
 should have one :-)




Sure I'd do something like that! Maybe refering to the Ali 
Çehreli's book!
Question is if my English skills are sufficient..

They aren't in the list because right now nothing is written in D 
in our company. But the future will look different I according to 
what my dad told me.

Is there a reddit community? How is D generally seen in the 
internet?
Jul 31 2015