Chapter 6 Flashcards by jaco smith

What does a data type define?

Collection of data objects with a range of value and how they are stored in memory.

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What does an object represent?

The instance of a programmer-defined type

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What is another name for a programmer-defined type?

Abstract data type

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Do all languages provide primitive data type?

Almost all of them

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What is special about Integers?

It is an exact reflection of the hardware therefore mapping is trivial

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How many different integer types are there?

May be as many as eight

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What are the advantages of unsigned integers?

It cant go below 0. So you can store a lot more data into the field

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Do Floating points model real numbers?

Yes but only as approximations

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What are the 2 floating point types?

float and double

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What is the standard for floating points?

IEEE Floating-Point Standard 754

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How many bits does double and float use?

double = 64 bits
float = 32 bits
for both 1 bit = signed bit

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in complex data types, what makes up each value?

a real part and an imaginary part (7 + 3j where 7 = real and 3 = imaginary

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Whats the advantages and DisAdv of decimals

Adv : accuracy
DisAdv : waste memory and limited range

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Why is an advantage of boolean values readability?

Simplicity and clear representation

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How is the primitive data type character stored?

numeric codings with most common being ASCII

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What are the different types of character encodings of primitive data types?

ASCII, UCS-2 (16 bit),32-bit Unicode(UCS-4)

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How are lists represented and what do they hold?

ordered sequence of (often) heterogeneous values
Typically represented as a linked list

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How does lists look like in F#?

[1;2;3]

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What does F# list functions have in common with Scheme?

List.head [1;2;3] is equal to car (only returns the 1st element = 1)
List.tail [1;2;3] is equal to cdr in scheme (returns the rest of the list besides the head = [2;3]

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Are Python lists mutable and what does it mean?

Yes. allows [3, 5.8 ,”grape”]

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How do you delete list elements in Python?

del myList[1]

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How does list comprehensions look like in Python?

list = [x ** 2 for x in range(12) if x % 3 == 0]

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Where is Type theory studied in?

Math, Logic, CS, Philosophy

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What is a union?

Study These Flashcards

A type whose variables can store values of different types at different times during execution

How many values can be assigned to a union at once?

What are union types used for?

Representing Values with Multiple Possibilities

What is the difference between Discriminated vs Free Unions

Disc = type checking, higher type safety, runtime errors less likely, clearer readability. free = no type checking, lower type safety, runtime errors more likely, less clear readability

union example in C

union flexType{ int intEl; float floatEl; }; union flexType u1; u1.intEl = 12; u1.floatEl = 22.8; float x = u1.floatEl; int y = u1.intEl;

Example of Discriminant

type Shape is (Circle, Triangle, Rectangle); type Colors is (Red, Green, Blue); type Figure (Form: Shape) is record Filled: Boolean; Color: Colors; case Form is when Circle => Diameter: Float; when Triangle => Leftside, Rightside: Integer; Angle: Float; when Rectangle => Side1, Side2: Integer; end case; end record; "Form" is the discriminant

Why are free unions unsafe?

They do not allow type checking

Are Ada's discrimination unions safe?

Yes

What are pointer type variables?

memory addresses that reference a memory (nil/null = doesnt refer to a memory cell)

What are the 2 uses of pointers?

power of indirect addressing manage dynamic memory

What is the scope and lifetime of a pointer?

Scope = if declared inside function == only accessible in that function. if declared globally == anywhere lifetime = until memory location it is pointing to isnt valid anymore

What is the lifetime of a heap-dynamic variable?

Until the user deletes it, otherwise it will result in memory leaks declared using "new" in c++

Are pointers restricted as to the type of value to which they can point?

Yes. For type safety and memory management

Are pointers used for dynamic storage management, indirect addressing, or both?

Both

Should the language support pointer types, reference types, or both?

Depends. If type safety needed = reference types

What are the 2 fundamental operations for pointers?

Assignment and dereferencing int *p = &val; j = *ptr <- deref

What is the problem with pointers?

Dangling pointers (seg-faults/memory corruption) Lost heap-dynamic variable (allocated heap-dynamic variable that is no longer accessible = memory leaks)

What are reference type?

Similar to pointers but no pointer arithmetic allowed

Is reference types or pointers safer?

Reference types

What is the main purpose of reference types?

For parameters void f(int &p){...}

How does Java extend C++ reference variables?

Allows them to replace pointers entirely references can refer only to object and not primitives

What need to be done on pointers if they are used for dynamic storage management?

manual heap management is necessary

Why cant pointers and references not be avoided?

need them for dynamic data structures

What is type checking?

ensuring operands of an operator are of compatible types

What is a compatible type?

Type that is either legal for the operator or is allowed under language rules to be converted by compiler

What is a type error?

Application of operator to an operand of inappropriate type

If all type bindings are static can nearly all type checking be static and why?

Yes. It tells the compiler the types upfront

What is the Adv of a strongly typed language?

Detects all variable misuses causing type errors

Out of the following languages which are strongly typed? C C++ Java C# ML and F#?

Java C# ML and F# with ML and F# being very strongly typed

What are coercion and what does it do to typing

converts operands to same type and it causes type weakening since it can cause accidental type mismatches go undetected

Which languages use coercions?

C++ Ada and Java

What is type equivalence?

It defines when operands of 2 types can be substitutable with no coercion

When are 2 variable name type equivalent?

Same declaration or declarations that use the same type name

When are 2 variable structure type equivalent?

If their types have identical structures

What are the 2 branches of type theory?

Practical (data types in commercial languages) Abstract (typed lambda calculus and of interest only to theoretical computer scientists)

What is a type system?

A set of types and rules that govern type use in programs

Chapter 6 Flashcards

(59 cards)