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[6 pts]
Tabulate the values taken on by i, j, and k
as the program fragment below executes.
j = 1
k = 1
for i in range(4):
k = k + i * j
j = i
[6 pts]
Convert the below to an equivalent if statement where
not doesn't appear.
if not (a == b and b >= c):
[8 pts] What is displayed when the below program is executed?
def run():
a = 1
y = 2
b = process(a)
c = process(b)
print a, b, c
print y
def process(x):
y = x + 1
x = x * 2
print y
return x
run()
[10 pts]
Complete the below function so that it returns the smallest
positive number in its parameter list. For example,
min_positives([5, 2, -1, 3]) should return 2. You can
assume the list has at least one positive number, which will be less
than 999.
def min_positives(nums):
[8 pts] Give a derivation or syntax tree for b a b b using the below context-free grammar.
| S | → | A a | b A |
| A | → | a S | A b | a |
[8 pts] Write a context-free grammar describing the language containing all strings of a's and b's in which every a has a b just after it. Examples include abbab, bbabb, and bbbb, but not bbba or abbaab.
[10 pts] The file words.txt is a file containing several lines with one English word on each line. Complete the below Python fragment so that it displays all six-letter words beginning with q.
dictionary = open('words.txt')
[8 pts] What is displayed when the below program is executed?
nums = [7, 9, 6, 7, 8]
map = {}
for i in range(5):
n = nums[i]
map[n] = i
for key in map:
print key, 'to', map[key]
[8 pts] In the context of networking, why do messages typically include port numbers rather than simply the computers' IP addresses?
[8 pts] Suppose you tell your Web browser to retrieve the page http://ozark.hendrix.edu/~burch/cs/150/. Using HTTP, what message might the Web browser send to ozark.hendrix.edu to retrieve the requested Web page?
i: | 0, | 1, | 2, | 3 | |
j: | 1, | 0, | 1, | 2, | 3 |
k: | 1, | 1, | 1, | 3, | 9 |
if a != b or b < c:
2 3 1 2 4
def min_positives(nums):
min = 1000
for n in nums:
if n > 0 and n < min:
min = n
return min
|
|
for line in dictionary:
word = line.rstrip()
if len(word) == 6 and word[0] == 'q':
print word
7 to 3 9 to 1 8 to 4 6 to 2
A port number, allocated uniquely on the computer for each program running, allows a sender to identify the particular program on the destination computer that should receive the message.
Following is a minimal example of the text the browser might send to the Web server:
GET /~burch/cs/150 HTTP/1.1
Host: ozark.hendrix.edu
[an empty line signals the end of the request]