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The program is written using characters that are defined by the lexical structure of the language used. The character set is equivalent to the alphabet used by any written language. The lexical grammar lays down the rules governing how a character sequence is divided up into subsequences of characters, each part of which represents an ...
Tools have been written that automatically generate a lexer from a lexical specification written in regular expressions and a parser from the phrase grammar written in BNF: this allows one to use declarative programming, rather than need to have procedural or functional programming. A notable example is the lex-yacc pair.
In lexicography [citation needed], a lexical item is a single word, a part of a word, or a chain of words that forms the basic elements of a language's lexicon (≈ vocabulary). [ citation needed ] Examples are cat , traffic light , take care of , by the way , and it's raining cats and dogs .
Examples of fields: name, gender, hair colour. filename extension An identifier specified as a suffix to the name of a computer file. The extension indicates a characteristic of the file contents or its intended use. filter (software) A computer program or subroutine to process a stream, producing another stream.
Additionally, there are also informal criteria one can use in order to determine syntactic categories. For example, one informal means of determining if an item is lexical, as opposed to functional, is to see if it is left behind in "telegraphic speech" (that is, the way a telegram would be written; e.g., Pants fire. Bring water, need help.
In computer programming languages, an identifier is a lexical token (also called a symbol, but not to be confused with the symbol primitive data type) that names the language's entities. Some of the kinds of entities an identifier might denote include variables, data types, labels, subroutines, and modules.
Examples of approaches within structural semantics are Lexical field theory (1931-1960s), relational semantics (from the 1960s by John Lyons) and componential analysis (from the 1960s by Eugenio Coseriu, Bernard Pottier and Algirdas Greimas). [1] From the 1960s these approaches were incorporated into generative linguistics. [1]
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).