CPSC_103_Midterm_2021W1_Solution-1

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University of British Columbia *

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103

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Apr 3, 2024

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2021W1 Midterm Answer Key Question 1 numbers = [2, 3, 2, 7, 4, 3] tot = 0 for i in numbers: if is_even(i): # assume is_even(i) is a function that is # complete and correct (and available for use) # is_even(i) returns True if i is even tot = tot + i tot 8 Question 2 def foo1(x): return x/2 def foo2(x, y): y = 20 x == y x = foo1(y) y = 3 return x foo2(6, 5) 10 Page 1 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key Question 3 The Beverage data below (similar to the one you saw in Worksheet 4) records information about a beverage offered at the cafe, including: ● Its name, as it appears in the menu ● Its price ● Whether or not it is dairy-free Even though this data definition will run with no errors, there are some errors in the data design. Identify the line number where each error is found and describe how you would fix each error. For example, if you believe a line should be removed, write its number and SHOULD BE REMOVED after it (capitalization does not matter) (i.e., Line 7 should be removed or LINE 7 SHOULD BE REMOVED). 01. from typing import NamedTuple 02. Beverage = NamedTuple( 'Beverage' , [( 'name' , str ), 03. ( 'price' , float ), 04. ( 'dairy_free' , str )]) 05. 06. #interp. a beverage available in the cafe’s menu, 07. # including its name, price, and whether or not it is dairy free. 08. 09. BLACK_COFFEE = Beverage( "Black coffee" , 2.50 , "Yes" ) 10. EARL_GRAY = Beverage( "Earl Gray Tea" , 3.25 , "Yes" ) 11. LONDON_FOG = Beverage( "London Fog" , 4.75 , "No" ) 12. 13. # template based on compound (3 fields) 14. @typecheck 15. def fn_for_drink (b: Beverage) -> ... : 16. return ... (b . name, 17. b . price) Line 3: an interval comment is needed to show that price cannot be a negative number Line 4: dairy_free should be a bool, not a str Lines 9-11: The “Yes” should be changed to True and the “No” should be False Line 15: It should be fn_for_beverage , not fn_for_drink Line 18: Missing a b.dairy_free in the data template. Page 2 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key Question 4 Time to work on a classic RPG game! Design a data type for a character in a game. A character’s information is comprised of: ● Its name ● Its race (one of: human, elf, dwarf, ogre) ● Its health points (between 0 and 300) ● Its mana points (between 0 and 300) The data definition for race is already given to you: from enum import Enum Race = Enum("Race", ["HUMAN", "ELF", "DWARF", "OGRE"]) # interp. The possible races for a character in the game # examples are redundant for enumerations @typecheck # Template based on Enumeration (4 cases) def fn_for_race(r: race) -> ...: if r == Race.HUMAN: return … elif r == Race.ELF: return … elif r == Race.DWARF: return ... elif r == Race.OGRE: return ... Page 3 of 12 No Unauthorized Distribution of Materials

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2021W1 Midterm Answer Key from typing import NamedTuple Character = NamedTuple(‘Character’, [(‘name’, str), (‘race’, Race), (‘health’, int) # in range [0,300] (‘mana’, int) # in range [0,300]]) # interp. information about a character in the RPG game, # including name (name), race (race), health points # (health), and mana points (mana). CH1 = Character(“Raghard”, Race.Human, 150, 100) CH2 = Character(“Wargo”, Race.Ogre, 0, 300) CH3 = Character(“Oggy”, Race.Dwarf, 300, 0) # template based on compound (4 fields) and reference rule @typecheck def fn_for_character(c: Character) -> ...: return ...(c.name, fn_for_race(c.race), c.health c.mana) Page 4 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key Data Definitions Used in Questions 5 and 6 Type = Enum("Type", ["APARTMENT", "HOUSE"]) # interp. Property type. It can be an apartment or a house. # Examples are redundant for enumerations # template based on Enumeration @typecheck def fn_for_type(t: Type) -> ...: if t == Type.APARTMENT: return ... elif t == Type.HOUSE: return ... Property = NamedTuple("Property", [("type", Type), ("square_feet", int), # in range (0,...) ("year", int), ("price", int), ("pending", bool)]) # interp. information about a property, including its type # (apartment or house), footage, the year it was built, # price and whether or not it has a pending offer. P1 = Property(Type.APARTMENT, 625, 2020, 450000, False) P2 = Property(Type.HOUSE, 1100, 1980, 1350000, False) P3 = Property(Type.HOUSE, 925, 1995, 1100000, True) # template based on Compound and reference rule @typecheck def fn_for_property(p: Property) -> ...: return ...(fn_for_type(p.type), p.square_feet, p.year, p.price, p.pending) Page 5 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key # List[Property] # interp. a list of properties in the agency’s inventory L0 = [] L1 = [P1, P2, P3] # template based on arbitrary-sized and reference rule @typecheck def fn_for_lop(lop: List[Property]) -> ...: # description of the accumulator acc = ... # type: … for p in lop: acc = ...(fn_for_property(p), acc) return ...(acc) Page 6 of 12 No Unauthorized Distribution of Materials

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2021W1 Midterm Answer Key Question 5 The data definitions on the previous two pages are for a Real Estate agency that deals in private homes. Each property has a type (apartment or house), square feet, year built, price, and a status to indicate whether or not an offer is pending on it. The following function examines a list of properties to determine whether or not it contains a house that costs at most $1000000 and is of a given footage or greater. Complete the helper functions and add new ones if needed. You can assume has_cheap_house_min_footage() is complete and correct. Be sure to follow the HtDF recipe. You are allowed to assume that the tests for all functions in this question are present, complete, and correct. from cs103 import * @typecheck def has_cheap_house_min_footage(lop: List[Property], sf: int) -> bool: """ Returns True if there is at least one house of footage equal or greater than sf that costs at most one million dollars in the list; False otherwise. """ # return True # stub # template copied from List[Property] with 1 # additional parameter for p in lop: if is_property_house(p) and has_min_footage(p, sf) and costs_at_most_one_million(p): return True return False # Complete the helper functions below and add new functions if needed # Be sure to follow the FULL HtDF recipe Page 7 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key @typecheck def is_property_house(p: Property) -> bool: """ Returns True if p is a house; False otherwise. """ # return True # stub # template based on Property # return is_house(p.type) @typecheck def is_house(type: Type) -> bool: """ Returns True if type is Type.HOUSE; False otherwise. """ # return True # stub # template based on Type if type == Type.APARTMENT: return False elif type == Type.HOUSE: return True @typecheck def has_min_footage(p: Property, square_footage: int) -> bool: """ Returns True if p's square footage (i.e., size) is at least square_footage large; False otherwise. """ # return True # stub # template based on Property with additional parameter return p.square_feet >= square_footage Page 8 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key @typecheck def costs_at_most_one_million(p: Property) -> bool: """ Returns True if p costs one million dollars or less; False otherwise. """ # return True # stub # template based on Property return p.cost <= 1000000 # You are allowed to assume that all tests required for the # functions above are present, complete, and correct Page 9 of 12 No Unauthorized Distribution of Materials

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2021W1 Midterm Answer Key Question 6 Consider the Real Estate agency data definitions given earlier. We want to design a function to return all apartments built after a given year and below a given price. Here are some functions which may or may not prove useful. It is possible that your answer will not call every helper function listed in this question. You cannot write any other function for this question. Only use what you are given. You do NOT need to provide a complete implementation of the helpers. You only need to complete find_apartments_by_year_and_price(). You do not need to provide tests for find_apartments_by_year_and_price(). @typecheck def find_all_apartments(lop: List[Property]) -> List[Property]: """ Returns all apartments in lop. """ return [] # stub @typecheck def is_property_apartment(p: Property) -> bool: """ Returns True if p is an apartment; False otherwise. """ # return True # stub @typecheck def is_apartment(t: Type) -> bool: """ Returns True if t represents an apartment; False otherwise. """ # return True # stub Page 10 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key @typecheck def find_properties_in_budget(lop: List[Property], p: int) -> List[Property]: """ Returns all properties with price equal to or below p. """ return [] # stub @typecheck def is_property_in_budget(p: Property, pr: int) -> bool: """ Returns True if the property p has price equal to or below pr; False otherwise. """ # return True # stub @typecheck def find_properties_built_after_year(lop: List[Property], y: int) -> List[Property]: """ Returns all properties built strictly after year y. """ return [] # stub @typecheck def is_property_built_after_year(p: Property, y: int) -> bool: """ Returns True if the property p was built strictly after year y; False otherwise. """ # return True # stub Page 11 of 12 No Unauthorized Distribution of Materials

2021W1 Midterm Answer Key @typecheck def find_apartments_by_year_and_price(lop: List[Property], y: int, p: int) -> List[Property]: """ Returns a list of all apartments built after a given year (y) and below a given price (p). """ # return [] # stub # template based on composition # 1. filter all apartments # 2. filter all apartments built after year y # 3. filter all apartments built after year y with # price equal or less than price p # 4. return final list # Complete the rest of the # find_apartments_by_year_and_price function all_apartments = find_all_apartments(lop) apartments_after_year = find_properties_built_after_year(all_apartments, y) apartments_at_most_price = find_properties_in_budget(apartments_after_year, p) return apartments_at_most_price Page 12 of 12 No Unauthorized Distribution of Materials

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