perl problems

[SimpleWater]

So i have been reading tons of tutorials across the net. Anyways, i would like to request that someone create a thread dedicated to perl questions, as i get stuck very often :p

While i was trying to see if i can make a very simple quiz, it fails. why?

#!/usr/bin/perl
use strict;
use warnings;
use 5.010;

print "What is the largest desert in the world? ";
if (<stdin>eq"sahara") {say "correct!";}
else {say "incorrect";}

why is it when i am asked the question, and type in exactly sahara, i get incorrect always. sahara is the correct answer. Can someone help me with the syntax?

[L18L]

Are you sure your input is exactly sahara ?
Maybe there is trailing something like newline.
Try to chop the input.
Hope that helps

Note, I have never used or learnt pearl.
But the same has to be done in BaCon

[SimpleWater]

I did try chop and chomp, and i got the same results

[2lss]

Do you know what variable type stdin represents? i.e. integer, or string?

Since "sahara" is quoted, it probably represents a string in the eyes of the interpreter.

You could be comparing two different types of variables.

But I know little about perl so its just a guess.

[L18L]

try this:
http://www.lehrer.uni-karlsruhe.de/~za1 ... perl01.htm
found this by searching: perl chop stdin
Your result might vary dependent of your language

[SimpleWater]

try this:
http://www.lehrer.uni-karlsruhe.de/~za1 ... perl01.htm
found this by searching: perl chop stdin
Your result might vary dependent of your language

I guess you expect me to learn a whole new language eh? I have done multiple searches on chop though.

hello 2lss,

I had a hard time following, i know it is an alphabetical string. Now what?

[L18L]

I guess you expect me to learn a whole new language eh? I have done multiple searches on chop though.

Wrong guess. You want learn a whole new language

http://www.wellho.net/mouth/255_STDIN-S ... ndles.html

http://www.wellho.net/mouth/2963_Removi ... ence-.html

That is not

tons of tutorials across the net

just 2 clicks

Good luck

Edited: You might ask here more specific
Did you read "chop-or-chomp-in-Perl-what-is-the-difference"
Reproduce that example?

[technosaurus]

shell is so much easier for me ... maybe someone could translate it to perl

Code: Select all

#!/bin/sh
#initialize variables (just in case)
numright=0
questions=0

ask() {  ##usage: ask "What is your question?" "correct answer"
#ask question and wait for an answer feel free to replace read with dialog/xdialog
read -p "$1 ?  " response 

#put in all lower case
answer=`echo $2 |tr [:upper:] [:lower:]`
response=`echo $response |tr [:upper:] [:lower:]` 

#check ans
[ "$response" == "$answer" ] && echo correct && numright=$(($numright+1)) || echo incorrect
}
IFS="
"
for oneline in `cat testfile`; do
  question=`echo $oneline |cut -d "|" -f 1`
  answer=`echo $oneline |cut -d "|" -f 2`
  ask "$question" "$answer"
  questions=$(($questions+1))
done

echo you got $numright out of $questions correct.

testfile should be in the working directory (unless you include the full path) and in the format:

• what is 1+1|2
  what is the square root of 9|3

[SimpleWater]

I can just leave this alone for now. Not all things are easier in the shell though, but i can agree on most. For example math:

perl:

Code: Select all

5+5

bash:

Code: Select all

((5+5))

[L18L]

shell is so much easier for me ... maybe someone could translate it to perl

SimpleWater,
technosaurus did not say that anything is easy in shell but it is easier for him

Anyway math in python is easy:
# python
Python 2.6.4 (r264:75706, Sep 13 2010, 13:05:58)
[GCC 4.3.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 5+5
10
>>>

[technosaurus]

SimpleWater,
technosaurus did not say that anything is easy in shell but it is easier for him

That's exactly what I meant. I haven't _had_ to use perl, so I don't.

btw here is the awk based function I normally use for doing in-shell calculations:

calc() {
awk "BEGIN{print $@}"
}

+,-,*,/,%,sqrt() ... any math functions that awk supports (and it can be a rather large set)

in fact here is the stupidest little calculator I've created

Code: Select all

#!/bin/sh
A=`awk "BEGIN{print $@}"`
A=`Xdialog --stdout --inputbox "Simple calculator" 0 0 $A`
[ $A ] && $0 $A

[akash_rawal]

I have no knowledge of perl, but by trial I found the fix.
I was sure that the trailing newline is the issue.

Code: Select all

#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
print "What is the largest desert in the world? ";
if (<stdin>eq"sahara
") {say "correct";}
else {say "incorrect";}

[L18L]

I have no knowledge of perl, but by trial I found the fix.
I was sure that the trailing newline is the issue.

Code: Select all

#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
print "What is the largest desert in the world? ";
if (<stdin>eq"sahara
") {say "correct";}
else {say "incorrect";}

+1
Now it will need just a chop so that it can be used in technosaurus' predefined list of question|answer.

what is 1+1|2
what is the square root of 9|3

---------------------------------------------
Edited:

One idea leads to another..

- Code a quiz in sh, bash4, perl, python,....,C, BaCon
- this on console and gui
- Use one an the same list of question|answers
- internationalization using GNU gettext
- localization (translating to human languages)
Learning from the different programming languages.
Take puppy related questions...
Puppy Certified [User|Administrator|Developer|Maintainer|Promoter|Tester|Translator|Troll]
Am I joking or not joking? That is the question.

[SimpleWater]

I have no knowledge of perl, but by trial I found the fix.
I was sure that the trailing newline is the issue.

Code: Select all

#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
print "What is the largest desert in the world? ";
if (<stdin>eq"sahara
") {say "correct";}
else {say "incorrect";}

Correct! Believe me there was plenty of trial going on here, but i guess that's not enough for someone with minimal experience. Thanks

L18L, interesting, but overwhelming. One language is trivial enough for me

[akash_rawal]

Believe me there was plenty of trial going on here, but i guess that's not enough for someone with minimal experience.

I am not one with minimal programming knowledge, I was aware of the trailing newline problem because in C, almost like in this case, function getline() returns a line of text from given stream with a trailing newline which has to be removed manually.

[L18L]

shell is so much easier for me ... maybe someone could translate it to perl
...

• what is 1+1|2
  what is the square root of 9|3

translated to BaCon

Code: Select all

'#!/bin/sh
'# technosaurus http://www.murga-linux.com/puppy/viewtopic.php?t=67704
' commented sh lines by apostroph in this 1st BaCon version by L18L

'#initialize variables (just in case)
numright=0
'questions=0

'ask() {  ##usage: ask "What is your question?" "correct answer"
FUNCTION ask(STRING q$, STRING a$)

 LOCAL response$
'#ask question and wait for an answer feel free to replace read with dialog/xdialog
'read -p "$1 ?  " response
 INPUT CONCAT$(q$, " ?  "), response$
'#put in all lower case
'answer=`echo $2 |tr [:upper:] [:lower:]`
 a$ = LCASE$(a$)
'response=`echo $response |tr [:upper:] [:lower:]`
 response$ = LCASE$(response$)

'#check ans
'[ "$response" == "$answer" ] && echo correct && numright=$(($numright+1)) || echo incorrect
 IF response$ != a$ THEN RETURN "incorrect"
 INCR numright
 RETURN "correct"

END FUNCTION
'}

'IFS="
'"

OPEN "testfile" FOR READING AS myfile
'for oneline in `cat testfile`; do
WHILE NOT(ENDFILE(myfile)) DO
 READLN oneline$ FROM myfile
 SPLIT oneline$ BY "|" TO quiz$ SIZE questions
'  question=`echo $oneline |cut -d "|" -f 1`
 question$ = quiz$[0]
'  answer=`echo $oneline |cut -d "|" -f 2`
 answer$ = quiz$[1]
'  ask "$question" "$answer"
 response$ = ask(question$, answer$)
 PRINT response$
'  questions=$(($questions+1))
'done
WEND
CLOSE FILE myfile

'echo you got $numright out of $questions correct.
PRINT numright, questions FORMAT "you got %1$d out of %2$d Questions correct."

testfile:

Code: Select all

What is the largest desert in the world|Sahara
what is 1+1|2
what is the square root of 9|3

Quirky detail: testfile mustnot have a blank line at the end
but bacon source must have a blank line at the end

Edited:
Load above BaCon code into a file, say quiz.bac in directory $HOME/programming/bacon
Get syntax Highlighting in geany by
Document > Set Filetype > Programming Languages > FreeBasic source file
(That is how I use it, there are better ways to do it e.g. NicoEdit see http://bkhome.org/bacon/gettingstarted.htm )

[Dud]

L18L was right to ask about line endings but akash_rawal's solution is, er, <shudder>, inelegant.

Here's an extended version of your script that demonstrates what's going on and uses chomp (intelligent chop) to remedy the problem. It also moves your check to a subroutine for multiple use.

#!/usr/bin/perl
use strict;
use warnings;
use 5.010;

print "What is the largest desert in the world? ";
my $reply=<stdin>;
say "\$reply contains: [$reply]";
saharacheck();

chomp ($reply);
say "After chomp \$reply contains: [$reply]";
saharacheck();

print "OK, this is another way to do it:\nWhat is the largest ocean in the world? ";
$reply=<stdin>;
if ($reply =~ /pacific/i){
say "correct!";
} else {
say "incorrect";
}

exit(0);

sub saharacheck{
print "Using old comparison: ";
if ($reply eq "sahara") {say "correct!";}
else {say "incorrect";}
}


Now here's how I might approach the task with more functionality, 'though this is left a little long-winded to aid comprehension:

#!/usr/bin/perl
use strict;
use warnings;
use 5.010;

question("What is the largest desert in the world?","sahara");
question("What is the largest ocean in the world?","pacific");

exit(0);

sub question{
my ($q, $a)=@_;
state ($right, $count);
$right+=0; # initialise in case the first answer is wrong
$count++;
print "$q ";
my $reply=<stdin>;
if ($reply =~ /$a/i) { # case insensitive regex match
print "Correct";
$right++;
} else {
print "Wrong";
}
print ", the answer is \u$a. Score: $right/$count\n";
}


# ./quiz.pl
What is the largest desert in the world? It's Sahara, I think.
Correct, the answer is Sahara. Score: 1/1
What is the largest ocean in the world? pacIFIC
Correct, the answer is Pacific. Score 2/2

Hth.

[SimpleWater]

Believe me there was plenty of trial going on here, but i guess that's not enough for someone with minimal experience.

I am not one with minimal programming knowledge, I was aware of the trailing newline problem because in C, almost like in this case, function getline() returns a line of text from given stream with a trailing newline which has to be removed manually.

I am sure you know much about programming. You see, that comment is towards me and not you, yes?

Yes i know how essential subroutines are Dud. Good for you to mention them, i see how i can optimize the code.

L18L, the name bacon just sounds interesting and also amusing

[L18L]

SimpleWater,
so you are motivated now to try your simple quiz in perl using a function ask and take the questions/answers from a text file?

BTW: Before I have never associated bacon other than "Sir Francis B."