Programming Language Concepts 2

Front 1

Compare system programming languages and scripting languages.

Back 1

System programming languages: Emphasize computing as a result. High-performance compilers.

Scripting languages: Emphasize automating as a process. Highly-portable interpreters

Front 2

What is a scripting language?

Back 2

A language that coordinates other programs

Examples:
A payroll system to process time data, scan paper forms, execute database queries, etc.
A photojournalism system that downloads pictures from a camera, converts them to a different format, process them, etc.
A dynamic web page that requires authentication, database lookup, remote communication, etc.

Front 3

Compare traditional programming languages and scripting languages.

Back 3

Traditional programming languages stress efficiency, maintainability, portability, and the static detection of errors
Types are built around hardware-level concepts such as fixed-size integers, floating-point numbers, characters, and strings

Scripting languages stress flexibility, rapid development, local customization, and dynamic runtime checking
Types are built around high-level concepts such as tables, patterns, lists, and files

Front 4

What are the common characteristics of a scripting language?

Back 4

Both batch and interactive use
Economy of expression
Lack of declarations; simple scoping rules.
Flexible dynamic typing
Easy access to other programs
Sophisticated pattern matching and string manipulation
High level data types

Front 5

What are the four advantages of Lua?

Back 5

Extensibility, simplicity, efficiency, and portability

easy to write modules that add functionality

easy to embed Lua as a scripting language in another program such as a game or use it on a hardware device

Front 6

A Lua variable names a function, but it never holds...

Back 6

the function itself, it only holds a reference to that function.

Front 7

Copying tables in Lua by passing them with their variable names...

Back 7

never happens. A variable cannot hold the table itself, it will just hold a reference to a table
This means that passing a table to a function or assigning a table to a new variable does not copy the table.

Front 8

What are closures and upvalues in Lua?

Back 8

A function that preserves the context that it was created in is called a closure
The preserved variables that can be accessed by closures are called upvalues
So a closure is a function that is bound by its scope, preserving local variables accessed by the function

Executing a function() ... end expression generates a new closure of that function
The original function acts as a prototype for that closure

Front 9

What does static typing mean?

Back 9

The compiler can do all the checking at compile time

Front 10

A collection of features is orthogonal if...

Back 10

there are no restrictions on the ways in which the features can be combined (similar to the idea of vectors in a multi-dimensional space)

Front 11

What is an ordinal type?

Back 11

A type in which the range of possible values can be easily associated with the set of positive integers

Front 12

What is an union?
What is a record?

Back 12

Union (variant record): a collection of fields where only one fields is valid at any given time
Record: a collection of fields, each of which belongs to a potentially different type

Front 13

A union's variables are allowed to...

Back 13

store different type values at different times during execution

Front 14

Different types of arrays

Back 14

Static: subscript ranges are statically bound and storage allocation is static (before run-time)

Fixed stack-dynamic: subscript ranges are statically bound, but the allocation is done at declaration time

Stack-dynamic: subscript ranges are dynamically bound and the storage allocation is dynamic (both are done at run-time)

Fixed heap-dynamic: similar to fixed stack-dynamic: storage binding is dynamic but fixed after allocation (i.e., binding is done at runtime, and storage is allocated from the heap, not the stack)

Heap-dynamic: binding of subscript ranges and storage allocation is dynamic and can change any number of times

Front 15

What is an associative array?

Back 15

an unordered collection of data elements that are indexed by an equal number of values called keys

Front 16

What is a dangling pointer?

Back 16

A pointer that contains the address of a heap-dynamic variable that has been deallocated

Front 17

Two fundamental abstraction facilities in programming languages

Back 17

Data abstraction: Emphasized in programming languages from the 1980s
The essence of code reuse via object-oriented programming

Process abstraction: Emphasized from the early days of programming languages
The essence of code re-use via subprograms

Front 18

What are the two categories of subprograms?

Back 18

* Procedures are collection of statements that define parameterized computations

* Functions structurally resemble procedures but are semantically modeled on mathematical functions