CS 111 Quiz 2 god help me part 1

To create a custom data type with named fields. Groups pieces of related information together.

What is the purpose of a struct? define-struct

(define-struct russian-dance-team (nickname height coach lifts-per-program))

Give a correct example of creating a struct

No parenthesis separating the field names from the struct name itself

(define-struct cat (name breed color meow-volume)

Fix and explain:

(define-struct cat name breed color meow-volume)

Does not specify the type of item as struct, therefore cat seems like a variable

Fix and explain:

(define cat (name breed color meow-volume))

the inner 2 arguments are not defined as lists, so they are passed as function or variable inputs instead.

List of lists, nested lists. Explain and fix

(define list-of-lists (1 2) (3 4))

No parenthesis necessary at *, 1 is taken as the accumulator start value. But outer list needs sub-lists, not numbers .

(map (lambda (xub) (fodll * 1 sub)) list-of-lists)

Nested lists, explain and fix

(foldl * 1 list-of-lists)

To extract and combine different parts of strings

What is the purpose of a substring and string-append function

(string-append "a" "n" "n" "a")

Write a correct example of string-append

Substring needs both a start and end indice, even if only producing one letter.

(substring "hello" 0 1)

Explain and fix

(substring "hello" 0)

Nothing! string-append doesn't need a parenthesis since it is a function being passed as an argument to foldl

Explain and fix

(foldl string-append "" (list "a" "b" "c"))

Libraries take lists of string input

(define pop-lib (list (make-track "living la vida loca" "ricky martin" "pop")))

Explain and fix this library

(define pop-lib (make-track "livin la vida loca" "ricky martin" "pop"))

Doesn't define the name of the struct. Needs to make-something for it to be findable as a "something"

(define latin-library (list (make-song "voy a reir" "marc anthony" "ice dance")))

Explain and fix this library

(define latin-library (list "voy a reir" "marc anthony" "ice dance"))

(define-struct track (title artist genre))

(list of track) -> (list of string) where all the strings are song titles,

Give the type signature of this function, which extracts all song titles from a library

(define all-titles

(lambda (lib)

(map track-title lib)))

(define-struct skating-programs (team year music))

Define a struct with a title and the input types

Not using the complete struct name.

(map (skating-programs-team name-of-new-list-here)

Fix and explain

(define-struct skating-programs (team year music))

(map programs team)

Should use map, not foldl. We are transferring items to a new list, not combining.

Fix and explain

(foldl skating-program-title empty lib)

(filter (lambda (t) (string=? team (track-year t))) name-of-a-new-list)

Use filter not map, because map returns booleans. Andmap returns a single boolean. Filter iterates through and edits the list.

Write a line of code from this struct that outputs a list of all the programs by a specific ice dance team

(define-struct skating-programs (team year music))

(map programs team)

(= (music (skating-programs-music "upbeat" library)) 2)

Write a boolean function to produce #true or #false from testing whether a team's music fits the upbeat 90s theme