Mimir:Draft6 Glossary

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  • BNF: In computer science, BNF (Backus Normal Form or Backus–Naur Form) is one of the two main notation techniques for context-free grammars, often used to describe the syntax of languages used in computing, such as computer programming languages, document formats, instruction sets and communication protocols; the other main technique for writing context-free grammars is the van Wijngaarden form. They are applied wherever exact descriptions of languages are needed: for instance, in official language specifications, in manuals, and in textbooks on programming language theory.
  • Conditionals: Conditionals are statements used to evaluate conditions on bases of true or false in order to perform different computations.
  • Cond: This function is like the IF statement in other languages and can take the form of an if-else-if statement. When Cond is called the first conditional statement will be evaluated and if true then the next part will be evaluated and so on to the last Atom which then becomes the returned value. If the first conditional statement is false the second conditional statement will be evaluated and so on until a conditional statement tests true. In the last conditional statement a T can be used to force TRUE condition and have a value returned.
  • Compiler: A compiler is a computer program (or set of programs) that transforms source code written in a programming language (the source language) into another computer language (the target language, often having a binary form known as object code). The most common reason for converting a source code is to create an executable program.

  • Data type: In computer science and computer programming, a data type or simply type is a classification identifying one of various types of data, such as real, integer or Boolean, that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of that type can be stored.
  • Dynamic language: A term used in computer science to describe a class of high-level programming languages which, at runtime, execute many common programming behaviors that static programming languages perform during compilation. These behaviors could include extension of the program, by adding new code, by extending objects and definitions, or by modifying the type system. These behaviors can be emulated in nearly any language of sufficient complexity, but dynamic languages provide direct tools to make use of them. Many of these features were first implemented as native features in the Lisp programming language.
  • Interpreter: In computer science, an interpreter is a computer program that directly executes, i.e. performs, instructions written in a programming or scripting language, without previously compiling them into a machine language program. An interpreter generally uses one of the following strategies for program execution:
    • parse the source code and perform its behavior directly
    • translate source code into some efficient intermediate representation and immediately execute this
    • explicitly execute stored precompiled code[1] made by a compiler which is part of the interpreter system

  • Imperative Paradigm: In computer science terminologies, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state.
  • Lists: A Lisp list is written with its elements separated by whitespace, and surrounded by parentheses. For example, (1 2 foo) is a list whose elements are three atoms: the values 1, 2, and foo. These values are implicitly typed: they are respectively two integers and a Lisp-specific data type called a "symbolic atom", and do not have to be declared as such.

The empty list () is also represented as the special atom nil. This is the only entity in Lisp which is both an atom and a list.

Expressions are written as lists, using prefix notation. The first element in the list is the name of a form, i.e., a function, operator, macro, or "special operator" (see below). The remainder of the list are the arguments. For example, the function list returns its arguments as a list, so the expression

(list '1 '2 'foo)

evaluates to the list (1 2 foo). The "quote" before the arguments in the preceding example is a "special operator" which prevents the quoted arguments from being evaluated (not strictly necessary for the numbers, since 1 evaluates to 1, etc.). Any unquoted expressions are recursively evaluated before the enclosing expression is evaluated. For example,

(list 1 2 (list 3 4))

evaluates to the list (1 2 (3 4)). Note that the third argument is a list; lists can be nested.

  • Paradigm: Paradigm is a model or a pattern by which a programming language constructs its programs. There are six main programming paradigms: imperative, functional, logic, visual, procedural, and object-oriented. Most of older languages are based on one of the paradigms, modern languages on the other hand are developed to include multiple paradigms.

  • Parsing: Parsing is an essential step for both Interpreters and Compilers. It is how we can pull text from files and make sense of it. This also means that it clearly defines the grammar for programming languages because how else can you parse it if you do not know the grammar for that language. That is the general purpose of most parser's but they also come with other features. A common feature is one where they check for correct syntax.
  • Regular expression: Regular Expressions (usually shortened to regex) is a sequence of characters that form a search pattern. This provides a common way of searching through strings. Regex's were created in the 1950s by an American mathematician named Stephen Kleene. In type three of Chomsky's Hierarchy the regular grammars use a similar system of terminals and non-terminals to Regex's.
  • Rule: Rule is a statement that tells you what is allowed or what will happen within a particular system.
  • Scanner: A scanner (lexical analyzer) is a function lex : string -> Lex.token list where Lex.token is a datatype of atomic symbols of the language.
  • Static Typed Language: Static typed programming languages are those in which variables need not be defined before they’re used. This implies that static typing has to do with the explicit declaration (or initialization) of variables before they’re employed. Java is an example of a static typed language; C and C++ are also static typed languages. Note that in C (and C++ also), variables can be cast into other types, but they don’t get converted; you just read them assuming they are another type.
  • Subroutine: Subroutines are blocks of code that performs a specific task. Once created they can be called multiple times within the program or implemented into other programs with ease. Subroutines eliminate code duplication, makes code cleaner, and easier to maintain.
  • Token: A "Token" is a single piece of data or an operator that has some meaning to the higher-level parser. The purpose of "Tokenizing" (creating tokens) is to remove unnecessary characters (spaces, line breaks, and so-on) from the input, and so substantially reduce the necessary complexity of the parser.A token can look like anything: English, gibberish symbols, anything; it just needs to be a useful part of the structured text.Tokens are frequently defined by regular expressions, which are understood by a lexical analyzer such as lex. The lexical analyzer reads in a stream of lexemes and categorizes them into tokens. This is called "tokenizing." If the lexer finds an invalid token, it will report an error.

  • Variable: In computer programming, a variable or scalar is a storage location paired with an associated symbolic name (an identifier), which contains some known or unknown quantity or information referred to as a value. The variable name is the usual way to reference the stored value; this separation of name and content allows the name to be used independently of the exact information it represents.
  • Variable Scope: The scope of a variable is what defines the availability of it during the executing of the program. Some programmers say that the scope of the variable is actually a property in it of itself. In other words, a variables scope is the area of a program where that specific variable has meaning and thus being visible to the code within that scope.