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String functions are used in computer programming languages to manipulate a string or query information about a string (some do both).. Most programming languages that have a string datatype will have some string functions although there may be other low-level ways within each language to handle strings directly.
A block is a grouping of code that is treated collectively. Many block syntaxes can consist of any number of items (statements, expressions or other units of code) – including one or zero.
The phrase grammar of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars, [8] though the overall syntax is context-sensitive (due to variable declarations and nested scopes), hence Type-1. However, there are exceptions, and for some languages the phrase grammar is Type-0 (Turing-complete).
The literature on programming languages contains an abundance of informal claims about their relative expressive power, but there is no framework for formalizing such statements nor for deriving interesting consequences. [52]
An abstract syntax tree (AST) is a data structure used in computer science to represent the structure of a program or code snippet. It is a tree representation of the abstract syntactic structure of text (often source code) written in a formal language.
A string grammar can be used to describe the structure of some natural languages, such as English or French, [2] [3] as well as for some computer languages. Note that the string-based structure is for defining the grammar of a language, rather than the formatting of the language itself.
It is decidable whether a given grammar is a regular grammar, [f] as well as whether it is an LL grammar for a given k≥0. [26]: 233 If k is not given, the latter problem is undecidable. [26]: 252 Given a context-free grammar, it is not decidable whether its language is regular, [27] nor whether it is an LL(k) language for a given k.
For instance, the lexical grammar for many programming languages specifies that a string literal starts with a " character and continues until a matching " is found (escaping makes this more complicated), that an identifier is an alphanumeric sequence (letters and digits, usually also allowing underscores, and disallowing initial digits), and ...