Assignment 25 — functional chrestomathics

Due Wednesday, April 1

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Requirements

• The buddy system is strongly encouraged.

• None of the functions should get input or print output.

• Examine and think about algorithms for the problems. However, do not write any code before class.

• The assignment module file magnificent.py will not be available to the start of class.

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Module magnificent.py

• Implements seven functions related to previous tasks performed this semester.

• Tester program seven.py performs basic testing of the module. It will not be available to the start of class.

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Function future_me( a, y )

• Returns how a person whose a years-old will be in the year y. You can assume the current year is 2020.

• Partial output from a sample run of seven.py

A 15 year-old will be 81 in 2086

A 19 year-old will be 98 in 2099

• Possible algorithm

• Compute difference between y and 2020.

• The difference added to a is the future age.

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Function manhattan_distance( a1, s1, a2, s2 )

• Returns the approximate distance in miles between a person at the corner avenue a1 and street s1 in Manhattan and a person at the corner of avenue a2 and street s2 in Manhattan.

• NYC distance rules:

• Distance of a Manhattan city block running from one street to the next is on average 1/20^th of a mile.

• Distance of a Manhattan city block running from one avenue to the next is on average 3/20^th of a mile.

• Partial output from a sample run of seven.py

Corners ( 6 , 59 ) and ( 7 , 34 ) are 1.4 miles apart

Corners ( 2 , 47 ) and ( 6 , 238 ) are 10.15 miles apart

• Possible algoithm

• Compute absolute value of the street differences

• Compute absolute value of the avenue differences

• The distance between the two locations is the street difference divided by 1/20 plus the avenue difference divided by 3/20

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Function relate( x, y )

• Returns 'comes before', 'is equal to', or 'comes after', depending whether the relationships between strings x and y are respectively:

• x alphabetically comes before y,

• x is equal to y, or

• x alphabetically comes after y.

• Partial output from a sample run of seven.py

kiwi is equal to kiwi

apple comes before banana

orange comes after melon

• Possible algorithm

• Determine which of x comes before (<) y, x equals y, or x comes after (>) y applies.

• Return respectively 'comes before', 'is equal to', or 'comes after' depending upon the possible relationships

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Function youngest( y )

• Returns the youngest acceptable age for a y-year old to date according to the dating folk rule you should only date someone who is at least seven years older than than half your age.

• Partial output from a sample run of seven.py

19 year old can date a 16 year old

22 year old can date a 18 year old

• Possible algorithm

• Compute and return y divided by 2 plus 7 using integer arithmetic

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Function is_dateable( y1, y2 )

• Returns True or False whether a y2-year old is an acceptably-aged date for a y1-year old.

• Your implementation should make use of function youngest().

• Partial output from a sample run of seven.py

15 year-old can date a 22 year-old is True

22 year-old can date a 15 year-old is False

19 year-old can date a 18 year-old is True

• Possible algorithm

• Determine minimum dateable age for y1

• Return whether or not y2 is at at least that minimum dateable age of y1

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Function mutually_dateable( y1, y2 )

• Returns True or False whether both a y2-year old is an acceptably-aged date for a y1-year old, and a y1-year old is an acceptably-aged date for a y2-year old

• Your implementation should make use of function is_dateable().

• Partial output from a sample run of seven.py

25 year-old can date a 65 year-old and vice-versa is False

20 year-old can date a 18 year-old and vice-versa is True

• Possible algorithm

• Determine whether or not y1 is dateable for y2

• Determine whether or not y2 is dateable for y1

• Return whether or not both dateable conditions are true

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Function middle( s )

• If the length of s is odd, the function returns the middle character of s; otherwise, the function returns the two middle characters of s.

• Partial output from a sample run of seven.py

Middle character of abcde is c

Middle character of abcdef is cd

Middle character of abcd is bc

• Questions

• Suppose n is the length of s.

• If n is odd, what is the middle index of s

• If n is even, what are the middle indices of s

• Possible algorithm

• Determine the length of s

• Determine whether that length is odd; that is, whether the remainder of that length divided by 2 is 1.

• Use you answers to the previous questions to get and return the character(s) at the indicated index(s).

 

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© 2020 Jim Cohoon

Resources from previous semesters are available.