Write a Math module to extend the Fixnum class. This module should provide two methods. First, a class method called pi that prints out the value of pi to two significant digits. Second, an instance method called squared that squares a number. E.g. when you are finished the following should be possible:

puts Fixnum.pi
# 3.14
puts 2.squared
# 4

Suppose you have a class that performs several expensive calculations. However, during the lifetime of an object, the result of the expensive calculation won't change. Therefore, you wish to ensure that each calculation is performed only once, and that result is cached. A simple technique for this would be as follows:

class Calculator
    def expensive_calc_one
        return @result1 unless @result1.nil?
       @result1 = # Do very expensive calculation.
    end

   def expensive_calc_two
        return @result2 unless @result2.nil?
       @result2 = # Do very expensive calculation.
    end
end

If this class contained many such expensive calculations, this memoization technique would become repetitive. Can you come up with a framework that reduces this repetition by allowing one to simply mark a method as memoized and no longer have to worry about manually handling the caching?

Bonus points: There is a flaw in the simple technique. Under one set of circumstances the caching will fail and repeated calls to expensive_calc_one will result in the expensive calculation being executed again and gain. When would this occur?

Suppose you have a database with two tables, employee and department (see below for exact schema). Write a SQL statement to answer the following questions:

1. Show a list of all employees that includes both the employee name and the department name.
2. Show a list of departments and include the number of employees in each department.
3. Show a list of all departments with no employees.
4. Show a list of departments with more than 2 employees
5. Show a list of departments that includes average and maximum salary in that department. Sort the list by the average salary.

Employee Table
---------------------
id
first_name
last_name
salary
department

Department Table
-----------------------
id
name

Using browser default CSS, hyperlinks are displayed with a blue underline. Suppose you are writing a website and instead, you wish the default to be bold red font, with no underline. What would you put in your stylesheet?

Now suppose that when the user hovers their cursor above the hyperlink you want the text to turn green. What would you add to your stylesheet?

Suppose you have two CSS rule sets defined .bold {font-weight: bold; } and .bordered {border: 2px solid #CCC;} Write an additional rule-set that selects elements that are both .bold and .bordered and changes the font color to red?

You have a class Parent with a virtual method a and a class Child that implements a. You also have a several functions:

void f1(Parent p) { p.a(); }
void f2(Parent* p) { p->a(); }
void f3(Parent& p) { p.a(); }

When called with a Child instance, which method will be invoked for f1, f2 and f3?

Explain in detail what the following C++ code does:

#include <iostream>
using namespace std;

template <class T>
T GetMax (T a, T b) {
  T result;
  result = (a>b)? a : b;
  return (result);
}

int main () {
  int i=5, j=6, k;
  long l=10, m=5, n;
  k=GetMax<int>(i,j);
  n=GetMax<long>(l,m);
  cout << k << endl;
  cout << n << endl;
  return 0;
}

Suppose you have the following array

stuff = [:dog,:cat,:orange,:banana]

1. How can you slice this array to create a new array [:cat,:orange]
2. Add the element :apple on to the end of the array.
3. Now take :apple back off again
4. Add the element :fish to the start of the array.
5. Now remove the element :fish.

Explain the difference between echo() and print() statement? When might you use one over the other?

Explain the difference between the following quoting in Python:

my_string = 'the cat sat on the mat'
my_string = "the cat sat on the mat"
my_string = """the cat sat on the mat"""
my_string = '''the cat sat on the mat'''

How do you share methods between different parts of your code in Ruby? Can you name three strategies for doing this? Discuss the pros and cons of each.

Explore the basics of the display attribute:

1. What are the possible values for the DISPLAY attribute?
2. What's the default value?
3. What the difference between display:none and visibility:hidden?

Explore the basics of the position attribute:

1. What are the possible values for the POSITION attribute?
2. What's the default value?
3. How does the browser decide where to position absolute elements?

Suppose I have the following Array of tuples

[ ['a',1], ['b',2], ['c','3' ]

How can I convert this to a Hash?

{ 'a' => 1, 'b' => 2, 'c' => 3}

Once I've written the algorithm, how would I make it generally available throughout my Ruby application?

Given the following C code:

struct department {
 char name[20];
 int id;
};

struct department d;

add a typedef to allow easy declaration of departments and add some code that uses the typedef.

What is a register variable in C? When would you use one? What is the downside of using this storage class?

What would the following C code print out?:

#include <stdio.h>

main()
{
  int i=2,j=3;
  i=j++ + i++;
  j=++j + ++i;
  printf("%d%d\n",i,j);
}

Explain what the following code does:

#include <stdio.h>

int main()
{
   int i;
   int *p;

   i = 2;
   p = &i;

   *p = 3;      

   printf("%d\n", i);

   return 0;
}

What is the difference between pointer and reference? Please describe the two main differences.

What will original and copy evaluate to in each of the following examples? Explain why there is a difference.

original = "hello"
copy = original
copy << " there"
puts copy
puts original

original = "hello"
copy = original
copy += " there"
puts copy
puts original

In each example below indicate whether or not we should be asserting true or false. (E.g. what should the ? be?).

Explain the difference between ==, eql and equal?

str1 = "chitter"
str2 = "chitter"

assert_equal ?, str1 == str2
assert_equal ?, str1.eql?(str2)
assert_equal ?, str1.equal?(str2)
assert_equal ?, str1.object_id == str2.object_id

sym1 = :chatter
sym2 = :chatter

assert_equal ?, sym1 == sym2
assert_equal ?, sym1.eql?(sym2)
assert_equal ?, sym1.equal?(sym2)
assert_equal ?, sym1.object_id == sym2.object_id

Start with an array of integers, 1 through 5. First, square all the elements in the array. Then, sum all the elements of the squared array.

Most languages have a built in sort method that will sort an array of strings alphabetically. Demonstrate how to sort an array of strings by the length of each string, shortest strings first.

Define the following object oriented concepts:

• Class, object (and the difference between the two)
• Instantiation
• Method (as opposed to, say, a C function)
• Static methods and classes
• Destructor/finalizer
• Inheritance
• Encapsulation
• Multiple inheritance (and give an example)
• Abstract class
• Interface/protocol (and different from abstract class)
• Method overriding
• Method overloading (and difference from overriding)
• Polymorphism (without resorting to examples)
• Method visibility (e.g. public/private/other)

Explain the difference between dropping a table, truncating a table and deleting all the rows in a table.

Explain each of these types of joins:

• Inner Join
• Outer Join
• Left outer join
• Right outer join
• Full outer join
• Cross join

Explain the difference between the SQL "where" and "having" clauses.

Explain what a database transaction is. When would you use one? What problems could you case by using one?

Explain what the following statements do:

1. ls mydir > foo.txt
2. ls mydir > foo.txt 2>&1
3. cat file1 file2 > file3
4. cat file1 file2 >> file3

Write the Bash statements to:

1. Create a new file called banana-file-names.txt with the concatenated contents of every file in the current directory that starts with "banana"
2. Create a new file called banana-file-content.txt with the concatenated contents of every file in the current directory that contains the word "banana"

Write the Bash statements to:

1. Count the number of files ending in .java, in the current directory that have the string "pumpkin" in the file contents?
2. Do the same, including files in any sub-directory (recursively)
3. Replace every occurrence of "pumpkin" with "banana" in each of the files

Explain what each of the following Bash statements does and the overall result:

$ (date ; ps -ef | awk ‘{print $1}’ | sort | uniq | wc -l ) >> processes.log

Explain what the following Bash command does:

find . -type f -atime -7 > /tmp/recent_files

How many ways can an argument be passed to a method. Explain each method.

What are different types of access modifiers? Explain what they do.

Explain final, finalize() and finally?

Explain what Garbage Collection does. How is it normally initiated? How could you force it to run? What problems can it cause?

Explain the difference between method overloading and method overriding

Explain thedifference between this() and super()

Name 3 top level class modifiers.

Explain the difference between an inner class and an anonymous class? When would you use these?

Explain what reflection is in Java and give an example of when you might use it.

What is an interface in Java? Give and example of where you might use one. How does this compare to inheritance?

Explain the difference between Integer and int in Java and when you would choose to use one over the other.

Can an inner class be defined inside a method? What variables can be accessed by that class?

What is __init__.py? Give an example of where you would use it.

Explain what a list comprehension is and write some code that illustrates an example use.

Explain the difference between a tuple and a list and give an example of where you would use each.

Explain what the following Python code does:

phrase = 'hello mommy'
print phrase[:4] + phrase[4:]

Write one line of readable Python code that will print the sum the integers from 1 to 100

Describe two ways to concatenate strings in Perl. Contrast and compare.

Describe what the following Perl code does:

#!/usr/bin/perl
$numArgs = $#ARGV + 1;
print "$numArgs\n";
foreach $argnum (0 .. $#ARGV) {
print "$ARGV[$argnum]\n";
}

Write code to print the contents of the following array in Perl:

@fruit = ('banana', 'orange', 'apple');

Explain what the following Perl code would output:

$banana = 2;
print "$banana\n";
print '$banana\n';

In Perl, how would you allow functions to have private variables that retain their values from call to call?

What is a common way of sending email from a Perl program?

Explain the terms static, final, and const

Explain the difference between require_once(), require() and include() and when you might use these

What is a Final class and where might you use one?

Explain the difference between pass by value and pass by reference in a C program. Write a short program that illustrates the difference.