Records

The structured type with named and typed fields: definition, dot notation access, array of records, nested records.

22 cards
5 topics
Free

Study this deck

The outline, topic by topic

Each topic is weighted the way the exam weighs it.

Concepts
Questions
Sort and link
Scenarios
Understand

A few cards from the deck

Record: what is it?
Show the answer
A composite piece of data made of several named values, possibly of different types, grouped under a single name.
A student (name, age, average) is a record. In C it is a struct; in Java, a class or a record; in Python, a data class.
What does this program print?

```python
from dataclasses import dataclass

@dataclass
class Student:
name: str
marks: list

students = [Student("Ana", [12, 15]), Student("Ben", [9, 14]), Student("Cleo", [17, 11])]
print(students[1].marks[0])
`
- 9
- 14
- 12
- Ben
Show the answer
9
students[1] is the second student (Ben), .marks his list [9, 14], [0] the first mark: 9. 14 would be marks[1], 12 the first mark of the first student.
In C, a record is declared with the keyword … and a field is accessed with the … character, as in p.x.
Show the answer
In C, a record is declared with the keyword struct and a field is accessed with the dot character, as in p.x.
Python and Java use the same dot notation for a field or an attribute. In C, with a pointer to the record, write p->x.
Field: what is it?
Show the answer
A named and typed value that is part of a record.
A field is identified by its name, whereas an array cell is identified by its number. In an array, all the cells have the same type; this is not required of fields.
A program keeps two parallel arrays, names and ages. After sorting names alphabetically, the ages no longer match the right people. Which solution fixes the problem at its root?
- Also sort ages, with the same algorithm, but on its own values
- One array of Person(name, age) records, sorted as a block
- Sort ages first, then names, so the indices line up
- A single array alternating a name, an age, a name, an age
Show the answer
One array of Person(name, age) records, sorted as a block
Parallel arrays rely on a convention: cell i of each array concerns the same person. Sorting only one breaks it. A record keeps name and age together, and moving a cell moves both.

Study this deck