Programming Language Principles - Overview

Front 1

What is a functional language? (in contrast to procedural)

Back 1

Languages that don't concern themselves with state and memory locations. Instead, they work exclusively with values, and expressions and functions which compute values.

The resulting programs are more declarative than procedural ones; i.e. they describe what is to be computed rather than how it should be computed.

Front 2

What are the 3 primary characteristics of the functional paradigm?

Back 2

1. Functions are first-class values
2. Higher-order functions
3. Repetition is expressed as recursion (rather than iteration).

Front 3

What order of evaluation is used in functional languages?

Back 3

Normal (lazy) order. Expressions are evaluated only when needed. This allows us to build infinite data structures, where only the parts we need are actually constructed.

Front 4

What is call-by-name evaluation?

Back 4

The arguments to functions are not evaluated at all — rather, function arguments are substituted directly into the function body

Front 5

What order of evaluation is used in imperative languages?

Back 5

Applicative order, an evaluation strategy in which the arguments of a function are evaluated as they are encountered.

Front 6

What is call-by-value?

Back 6

An evaluation strategy in which the argument expression is evaluated, and the resulting value is bound to the corresponding variable in the function

Front 7

What is call-by-reference?

Back 7

An evaluation strategy in which a function is passed an implicit reference to its argument rather than the argument value itself.

Front 8

What is copy-restore?

Back 8

A special case of call-by-reference where the provided reference is unique to the caller. If a parameter to a function call is a reference that might be accessible by another thread of execution, its contents are copied to a new reference that is not; when the function call returns, the updated contents of this new reference are copied back to the original reference ("restored").

Front 9

How does applicative order treat function terms?

Back 9

Reduces terms within a function body as much as possible before a function is applied.

Front 10

What is partial evaluation?

Back 10

An evaluation strategy in which any sub-expressions that do not contain unbound variables are evaluated, and function applications whose argument values are known may be reduced.

Front 11

What is encapsulation?

Back 11

It is both information hiding and protection.

Front 12

What is overriding?

Back 12

A type of polymorphism in which a child class overrides the method implementation of the parent class.

Front 13

What is polymorphic coercion?

Back 13

A type of polymorphism in which a primitive or object type is cast into being another primitive type or object type.

Front 14

What is parametric polymorphism (method overloading)?

Back 14

A type of polymorphism in which a class or classes implement methods that are the same except for the parameters passed to the method. Same name, different signatures.

Front 15

What is abstraction?

Back 15

An object-oriented concept which includes both inheritance and composition. With inheritance it involves working at the appropriate level of detail from dog to Lassie. With composition it involves breaking the object into parts such as a car is a body, wheels, seats, etc.

Front 16

What are operational semantics?

Back 16

Mathematically rigerous definition of the program functionality, such as lamda calculus. Permits formal analysis of a language through a state transition system.

Front 17

What are denotational semantics?

Back 17

A mathematical description of the meaning of a program.

Front 18

What are axiomatic semantics?

Back 18

A mathematically rigorous way of validating a program.

Front 19

5 principles of oo programming

Back 19

1. Objects

2. Abstraction
Composition

3. Polymorphism
Overloading/overriding

4. Inheritance
Subclassing

5. Encapsulation
Information hiding

Front 20

Abstraction

Back 20

Primarily defined by composition. A car is made up of a body, tires, and an engine.

Front 21

Polymorphism

Back 21

One name different meanings. Breaks down into overloading and overriding.

Front 22

Overloading

Back 22

Reusing the same name of a method with different parameters.

Front 23

Overriding

Back 23

Reusing the same method name in subclasses so that the subclass can perform a specific activity with that method.

Front 24

Decoupling

Back 24

Preventing interdependencies between objects.

Front 25

Inheritance

Back 25

Subclassing. Reusing all the abilities of parent classes in the child classes.

Front 26

Encapsulation

Back 26

Information hiding. Restricting access to the internal structure of an object.

Front 27

Modularity

Back 27

Allowing the reuse of code by creating modules that perform specific functions.

Front 28

Three properties of a first class value

Back 28

1) Passed as a parameter
2) Returned from a subroutine
3) Assigned to a variable

Front 29

Higher-order function

Back 29

Takes a function as an argument or returns a function as a result

Front 30

How can we get "infinite" data structures in functional languages?

Back 30

Using lazy evaluation (similar to normal order) and functions as first class values. For example, if we want a list of all the prime numbers, we can create it dynamically. We could store the structure as a list of prime numbers, with the last number being a function that generates the next prime number.

If, in general, only the first 5 prime numbers are used, this is efficient, and still handles cases where the first thousand prime numbers are used. In effect, we have ALL of the prime numbers, even though we're only storing a finite set at a time.