Class 29 — Wednesday April 1

Functionization

Social distancing — Does not mean we cannot share — Love, hopes, and friendship

It's April Fools Day — I am sorry for past pranks — And those yet to come

---

Look both ways

• Back or ahead

---

Zoom

• Link to live meeting MWF @ 2 PM.

---

Download now

• Module go.py

• Tester program forth.py

---

Download when asked

• Module quad.py

• Tester program riga.py

---

The teaching assistant staff

• I strongly appreciate and hope you do so too, the efforts of the teaching assistants in making CS 1112 work.

• Not just to Nadia for staffing our virtual lectern and Ryan for keeping me aware of the chat questions and comments you communicate during out meetings, but also to Ann, Cecilia, Hallie, Hannah, Hunter, Jacob, Jeanine, Rachel, Sophia, and Xavier for their great efforts in answering chat questions, holding office hours, and monitoring Piazza.

---

All members of the CS 1112 community — students and staff

• I thank all of you for giving CS 1112 your attention in this unsettled time. I hope you, and your family and friends are doing well. I want to believe in the power of collective thoughts and prayers, and you are in mine.

---

Agenda

• Being functional

• Better able to convert problem specifications dealing with strings into working functions

---

To Do

• Look over your artifacts.

• Complete Homework 26

• Preview Homework 27

• Continue to try CodingBat.

---

Some scary datasets

• NY Times COVID-19 USA County Incidents

• NY Times COVID-19 USA State Incidents

---

Test 2

• Will be April 20. The final will be optional. The grading percentages will be updated to

• Homework: 20%

• Test 1: 35%

• Test 2: 35%

• Test 3: 10%

---

Function separate( s )

• Parameter s is a string.

• The function returns a new list where each element in the list corresponds to a character of s.

• Suppose

s1 = "apple"

s2 = "banana"

s3 = "1"

s4 = ""

• The separate() tester when given those strings as arguments to the function should produce the following output.

separate( s1 ): ['a', 'p', 'p', 'l', 'e']

separate( s2 ): ['b', 'a', 'n', 'a', 'n', 'a']

separate( s3 ): ['1']

separate( s4 ): []

---

Function join( sl )

• Parameter sl is a list of strings.

• Returns a string composed of the strings in string list sl, where a blank is used to separate the strings from each other.

• Suppose

sl1 = ['a', 'p', 'p', 'l', 'e']

sl2 = [ 'wa', 'hoo', 'wa ' ]

• The join() tester when given those lists as arguments to the function should produce the following output.

join( sl1 ): 'a p p l e'

join( sl2 ): 'wa hoo wa '

---

Function ints( ns )

• Parameter ns is a string that composed of zero or more integer substrings and nothing else.

• The function returns a list of integers corresponding to the integer substrings in ns.

• FYI: The following strings do not meet the specification for the ints() parameter ns, as they all contain at least non-integer substring.

b1 = "abc"

b2 = "3 def 4 ghi"

b3 = "3.14"

• FYI: The following the variable definitions all meet the specification for the ints() parameter ns, as they are composed of zero or more integer substrings and nothing else.

ns1 = " 3 "

ns2 = "12 11 -63"

ns3 = "31 415 92 653 5 9"

ns4 = " "

• The ints() tester when given those strings as arguments to the function should produce the following output.

ints( ns1 ): [3]

ints( ns2 ): [12, 11, -63]

ints( ns3 ): [31, 415, 92, 653, 5, 9]

ints( ns4 ): []

---

Function parse_phone_string( pn )

• Parameter pn is a string representing a USA phone number with an area code but without a country code. The first three digits in pn are the area code; the next three digits in pn are the prefix; and the last four digits in pn are the line number.

• The function returns a three-element integer list. The first element of the list is the pn area code in integer form; the middle element of the list is the pn prefix in integer form; the last element of the list is the pn line number in integer form

• Consider the following phone number strings

pn1 = "(201) 867-5309"

pn5 = "8602941986"

pn3 = "21 25 55 2368"

pn4 = "888.799.9666"

• The parse_phone_string() tester when given those strings as arguments to the function should produce the following output.

parse_phone_string( pn1 ): [201, 867, 5309]

parse_phone_string( pn2 ): [860, 294, 1986]

parse_phone_string( pn3 ): [212, 555, 2368]

parse_phone_string( pn4 ): [888, 799, 9666]

---

Suppose the following constants are in effect

PUNCTUATION = '''!"#$%&'()*+,-./:;<=>?@[]^_`{|}~'''

WHITE_SPACE = ' \t\n\r\v\f'

EXTRANEOUS = PUNCTUATION + WHITE_SPACE

---

Suppose the following test case variable definitions are in effect

test1 = ['AbCdE', 'ABCDE', '!"#x$&)|}~', '- x -_', 'AAcc', ' ', 'x\n']

test2 = ['\tx X']

test3 = []

test4 = ['a', 'B', 'r', 'A', 'c', 'a', 'D', 'a', 'B', 'r', 'a']

---

Function canonical( strings )

• Returns a new list without duplicates whose elements are lower case versions of those in strings with leading and trailing extraneous characters stripped.

• Given the above definitions of test1, test2, test3, and test4, the following is the expected invocation results for canonical().

canonical( test1 ) = ['abcde', 'x', 'aacc', '']

canonical( test2 ) = ['x x']

canonical( test3 ) = []

canonical( test4 ) = ['a', 'b', 'r', 'c', 'd']

• To carry out this task does it matter the order that we do things? In other words,

• Does it make a difference which of the three activites we do first: removing duplicates, converting to lower case, or stripping?

---

Function lower( strings )

• Returns a new list whose elements are lower case versions of those in strings.

• Given the above definitions of test1, test2, test3, and test4, the following is the expected invocation results for lower().

lower( test1 ) = ['abcde', 'abcde', '!"#x$&)|}~', '- x -_', 'aacc', ' ', 'x\n']

lower( test2 ) = ['\tx x']

lower( test3 ) = []

lower( test4 ) = ['a', 'b', 'r', 'a', 'c', 'a', 'd', 'a', 'b', 'r', 'a']

---

Function strip( strings )

• Returns a new list whose elements correspond to the elements in strings with leading and trailing extraneous characters (punctuation or whitespace) removed.

• Given the above definitions of test1, test2, test3, and test4, the following is the expected invocation results for strip().

strip( test1 ) = ['AbCdE', 'ABCDE', 'x', 'x', 'AAcc', '', 'x']

strip( test2 ) = ['x X']

strip( test3 ) = []

strip( test4 ) = ['a', 'B', 'r', 'A', 'c', 'a', 'D', 'a', 'B', 'r', 'a']

---

Function unique( strings )

• Returns a new version of strings without any duplicate values.

• Given the above definitions of test1, test2, test3, and test4, the following is the expected invocation results for unique().

unique( test1 ) = ['AbCdE', 'ABCDE', '!"#x$&)|}~', '- x -_', 'AAcc', ' ', 'x\n']

unique( test2 ) = ['\tx X']

unique( test3 ) = []

unique( test4 ) = ['a', 'B', 'r', 'A', 'c', 'D']

---

 

---

 

© 2020 Jim Cohoon

Resources from previous semesters are available.