Test your skills (2005)

[wtd]

Try that again after:

Python:

foo.grades.append(100)

[wtd]

wtd wrote:

Here's a python question.

Python:

class Student(object):    def __init__(self, name, *grades):       self.name = name       self.grades = grades    def __str__(self):       return "%s has an average of %.2f" % (self.name, self.average_grade)

Add a single line of code which makes the above class work correctly. It must not only work, but also accurately report the student's average grade.

The solution:

Python:

class Student(object):    def __init__(self, name, *grades):       self.name = name       self.grades = grades    def __str__(self):       return "%s has an average of %.2f" % (self.name, self.average_grade)    average_grade = property(lambda self: float(sum(self.grades)) / len(self.grades))

[rizzix]

Write a Perl one-liner to print out the 8-12th lines of a file. (this means i should be able to execute the code with perl -e)

[wtd]

code:

perl -ne "BEGIN{$c=0}print if++$c>7&&$c<13" file_name_here

[rizzix]

hmm.. ok.. but may i add one more criteria?

Try and avoid the braces {}

[rizzix]

Write a Perl one-liner, but avoid using any {} blocks.

The one-liner should parse a file extracting all Java-like comments where nesting comments is not allowed. (i.e you can safely assume there are no nested comments)

Sample Input:

Java:

import java.awt.*; import javax.swing.*; public class test {      public static void main(String[] args) {          // insert your application initialization code here         JFrame frame = new JFrame("Test Application"); /* create a new JFrame */         Dimension screenSize = frame.getToolkit().getScreenSize();                 frame.getContentPane().add(new JLabel("Hello World!"));          frame.setBounds(screenSize.width/4, screenSize.height/4,                         screenSize.width/2, screenSize.height/2);         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         frame.setVisible(true); /* always the last SWING method in main*/      } }

Sample Output:

code:

6: insert your application initialization code here   7: create a new JFrame  14: always the last SWING method in main

[wtd]

The simplest way I can think of does involve using the BEGIN block again.

[wtd]

Language: O'Caml

code:

# let h = Hashtbl.create 10;; val h : ('_a, '_b) Hashtbl.t = <abstr> # Hashtbl.add h "foo" 42;; - : unit = () # Hashtbl.add h "bar" 27;; - : unit = () # h;; - : (string, int) Hashtbl.t = <abstr>

Now, we know that the Hashtbl module has a "fold" function which takes a function, a hashtable, and an initial value.

The function it takes accepts three arguments: the key of the current entry, the value of the current entry, and the "accumulator" value.

Knowing this, write an expression which retrieves the keys from "h" as a list of strings.

[rizzix]

rizzix wrote:

Write a Perl one-liner to print out the 8-12th lines of a file. (this means i should be able to execute the code with perl -e)

The solution...

Perl:

8 .. 12 and print while (<>)

[wtd]

rizzix wrote:

rizzix wrote:

Write a Perl one-liner to print out the 8-12th lines of a file. (this means i should be able to execute the code with perl -e)

The solution...

Perl:

8 .. 12 and print while (<>)

The parens shouldn't be necessary due to the way postfix loops work.

[rizzix]

yep... now solve the other one

[rizzix]

rizzix wrote:

Write a Perl one-liner, but avoid using any {} blocks.

The one-liner should parse a file extracting all Java-like comments where nesting /* */ comments is not allowed. (i.e you can safely assume there are no nested /* */ comments)

The Solution...

Perl:

(s|.*/{2}(.*)|$1| or s|.*/\*|| .. s|\*/.*||) and s|\s*|| and printf "%3d: %s", $., $_ while <>

Breaking it down...

First we match /* to */ and extract contents within // to \n with the following regexs:

Perl:

s|.*/{2}(.*)|$1|

Perl:

s|.*/\*|| .. s|\*/.*||

Note: we use the substitution since we are only interested in the content that lies within these delimiters.

Then we trim out the whitespace off the result:

Perl:

s|\s*||

Finally we print it:

Perl:

printf "%3d: %s", $., $_

[Hikaru79]

Holy mother of God. I'm oddly reminded of the bash.org quote that goes:

bash.org wrote:

s7ank: i want to be one of those guys that types
"s/j&jd//.^$ueu*///djsls/sm."
and it's a perl script that turns dog crap into gold.

[md]

My mind just went *boink*. You should really put warnings up before showing code like that...

[wtd]

Java TYS:

code:

import java.util.*; public class OldArrayListTest {    public static void main(String[] args) {       ArrayList a = new ArrayList();       a.add("hello");       a.add("world");    } }

Demonstrate the command that will compile this without warnings using the Java 1.5.0 compiler.