Term
Explain the following code snippet:
sum_1 :: Num a => [a] -> a
sum_1 a = foldl (+) 0 a |
|
Definition
sum_1 takes in an array of type a and returns an element of type a.
Produces a sum by adding them together from left (fold l) to right. If the (+) parameter were a different operator, it would perform a different operation |
|
|
Term
Explain the following code snippet:
sum_2 :: Num a => [a] -> a
sum_2 [] = 0
sum_2 (x : xs) = x + sum_2 xs |
|
Definition
| This is a for each loop that recursively adds up the sum; xs is rest(x) as I understand |
|
|
Term
| How do you declare an iterator in python? How would you employ that iterator in a try/except block? |
|
Definition
Example:
def sum_2 (a) :
s = 0
p = iter(a)
while True :
try :
s += p.next()
except StopIteration :
break
return s |
|
|
Term
| Write a sum function over a collection using a for each loop in python. |
|
Definition
def sum_1 (a) :
s = 0
i = 0
while i != len(a) :
s += a[i]
i += 1
return s
def sum_2 (a) :
s = 0
p = iter(a)
while True :
try :
s += p.next()
except StopIteration :
break
return s
def sum_3 (a) :
s = 0
for v in a :
s += v
return s |
|
|
Term
| Write a sum function using an operator in python. |
|
Definition
def sum_4 (a) :
return reduce(operator.add, a, 0) |
|
|
Term
| Write a recursive sum function in python that uses the code snippet (a[1:]) |
|
Definition
def sum_5 (a) :
if not a :
return 0
return a[0] + sum_5(a[1:]) |
|
|
Term
| Write a recursive sum function in python that uses an iterator (you will use an aux func) |
|
Definition
def sum_6_aux (p) :
try :
v = p.next()
except StopIteration :
return 0
return v + sum_6_aux(p)
def sum_6 (a) :
return sum_6_aux(iter(a)) |
|
|
Term
| What are the different ways of saying if/else in Haskell? |
|
Definition
f :: Int -> Int
f n =
if n < 0 then
-1
else if n > 0 then
1
else
0
| n < 0 = -1
| n > 0 = 1
| otherwise = 0
h (-2) = -1
h 3 = 1
h _ = 0 |
|
|
Term
private static void g (int[] p) {
++p[1];}
int a[] = {2, 3, 4};
g(a);
assert a[1] == ?????;
What evaluates to true? |
|
Definition
|
|
Term
How did Beck at Chrysler eliminate the need for exhaustive
specifications and a large 'quality assurance' team? |
|
Definition
| writing tests before writing code |
|
|
Term
What is the output of the following program?
a = [2, 3, 4]
b = a
b += [5]
print a is b
a = (2, 3, 4)
b = a
b += (5,)
print a is b |
|
Definition
|
|
Term
| What is the Java code for accessing an IllegalAccessException's superclass? What is that superclass? Name the classes that are 1 and 2 places up the inheritance hierarchy from IllegalAccessException's superclass |
|
Definition
IllegalAccessException.class.getSuperclass() == Exception.class
Exception.class.getSuperclass() == Throwable.class;
Throwable.class.getSuperclass() == Object.class; |
|
|
Term
| Name the three class hierarchical levels above NameError(the top one is object)? |
|
Definition
|
|
Term
| What is the complexity of inserting an element into a sorted array? What about a binary heap? |
|
Definition
|
|
Term
| What are the two most common problems with releasing changes? |
|
Definition
|
|
Term
What is required to be able to refer to a non-static member of class
(e.g. a non-static data member, a non-static method)? |
|
Definition
|
|
Term
What is required to be able to refer to a static member of class
(e.g. a static data member, a static method)? |
|
Definition
|
|
Term
| In Python, are parameters passed by value or by reference? What about Java? Define the differences |
|
Definition
Both are passed by value.
Pass-by-value
The actual parameter (or argument expression) is fully evaluated and the resulting value is copied into a location being used to hold the formal parameter's value during method/function execution. That location is typically a chunk of memory on the runtime stack for the application (which is how Java handles it), but other languages could choose parameter storage differently.
Pass-by-reference
The formal parameter merely acts as an alias for the actual parameter. Anytime the method/function uses the formal parameter (for reading or writing), it is actually using the actual parameter. |
|
|
Term
What does the following code print?
def try_to_change_list_contents(the_list):
print 'got', the_list
the_list.append('four')
print 'changed to', the_list
outer_list = ['one', 'two', 'three']
print 'before, outer_list =', outer_list
try_to_change_list_contents(outer_list)
print 'after, outer_list =', outer_list |
|
Definition
List is mutable and we are changing the object we are referring to.
before, outer_list = ['one', 'two', 'three']
got ['one', 'two', 'three']
changed to ['one', 'two', 'three', 'four']
after, outer_list = ['one', 'two', 'three', 'four'] |
|
|
Term
What happens in python when we try to change the reference that was passed in as a parameter?
def try_to_change_list_reference(the_list):
print 'got', the_list
the_list = ['and', 'we', 'can', 'not', 'lie']
print 'set to', the_list
outer_list = ['we', 'like', 'proper', 'English']
print 'before, outer_list =', outer_list
try_to_change_list_reference(outer_list)
print 'after, outer_list =', outer_list |
|
Definition
The original list remains unchanged.
before, outer_list = ['we', 'like', 'proper', 'English']
got ['we', 'like', 'proper', 'English']
set to ['and', 'we', 'can', 'not', 'lie']
after, outer_list = ['we', 'like', 'proper', 'English'] |
|
|
Term
In Java, what is the following statement equivalent to?
return (n < 0) ? -1 : (n > 0) ? 1 : 0;} |
|
Definition
if (n < 0)
return -1
else if (n > 0)
return 1
else return 0 |
|
|
Term
| What defines a tuple vs. a list? |
|
Definition
| A tuple is an immutable list. |
|
|
Term
| According to Extreme Programming, what should you do when you are working on a story unlike anything you have done before? Move through it very quickly or plan it out slowly and try to get it perfect the first time? |
|
Definition
|
|
Term
| In XP you should release _____ and _____ |
|
Definition
|
|
