Glossary Previous: TableofSym> * Next: Index> * Up: !Root> #Wrap on {fH2}Glossary{f} #Indent +4 #Indent Backus-Naur Form (BNF) #Indent +4 Formal method of specifying context-free grammars. BNF was first used in the {fCite}ALGOL-60{f} report, 1963. \*Note Languagean>: Languages and Context-Free Grammars. #Indent Context-free grammars #Indent +4 Grammars specified as rules that can be applied regardless of context. Thus, if there is a rule which says that an integer can be used as an expression, integers are allowed {fEmphasis}anywhere{f} an expression is permitted. \*Note Languagean>: Languages and Context-Free Grammars. #Indent Dynamic allocation #Indent +4 Allocation of memory that occurs during execution, rather than at compile time or on entry to a function. #Indent Empty string #Indent +4 Analogous to the empty set in set theory, the empty string is a character string of length zero. #Indent Finite-state stack machine #Indent +4 A ``machine'' that has discrete states in which it is said to exist at each instant in time. As input to the machine is processed, the machine moves from state to state as specified by the logic of the machine. In the case of the parser, the input is the language being parsed, and the states correspond to various stages in the grammar rules. \*Note Algorithm>: The Bison Parser Algorithm . #Indent Grouping #Indent +4 A language construct that is (in general) grammatically divisible; for example, `expression' or `declaration' in C. \*Note Languagean>: Languages and Context-Free Grammars. #Indent Infix operator #Indent +4 An arithmetic operator that is placed between the operands on which it performs some operation. #Indent Input stream #Indent +4 A continuous flow of data between devices or programs. #Indent Language construct #Indent +4 One of the typical usage schemas of the language. For example, one of the constructs of the C language is the {fCode}if{f} statement. \*Note Languagean>: Languages and Context-Free Grammars. #Indent Left associativity #Indent +4 Operators having left associativity are analyzed from left to right: {fEmphasis}a+b+c{f} first computes {fEmphasis}a+b{f} and then combines with {fEmphasis}c{f}. \*Note Precedencf>: Operator Precedence. #Indent Left recursion #Indent +4 A rule whose result symbol is also its first component symbol; for example, {fEmphasis}expseq1 : expseq1 ',' exp;{f}. \*Note Recursion>: Recursive Rules. #Indent Left-to-right parsing #Indent +4 Parsing a sentence of a language by analyzing it token by token from left to right. \*Note Algorithm>: The Bison Parser Algorithm . #Indent Lexical analyzer (scanner) #Indent +4 A function that reads an input stream and returns tokens one by one. \*Note Lexical>: The Lexical Analyzer Function {fCode}yylex{f}. #Indent Lexical tie-in #Indent +4 A flag, set by actions in the grammar rules, which alters the way tokens are parsed. \*Note LexicalTie>. #Indent Look-ahead token #Indent +4 A token already read but not yet shifted. \*Note LookAhead>: Look-Ahead Tokens. #Indent LALR(1) #Indent +4 The class of context-free grammars that Bison (like most other parser generators) can handle; a subset of LR(1). \*Note MysteryCon>: Mysterious Reduce\/Reduce Conflicts. #Indent LR(1) #Indent +4 The class of context-free grammars in which at most one token of look-ahead is needed to disambiguate the parsing of any piece of input. #Indent Nonterminal symbol #Indent +4 A grammar symbol standing for a grammatical construct that can be expressed through rules in terms of smaller constructs; in other words, a construct that is not a token. \*Note Symbols>. #Indent Parse error #Indent +4 An error encountered during parsing of an input stream due to invalid syntax. \*Note ErrorRecov>. #Indent Parser #Indent +4 A function that recognizes valid sentences of a language by analyzing the syntax structure of a set of tokens passed to it from a lexical analyzer. #Indent Postfix operator #Indent +4 An arithmetic operator that is placed after the operands upon which it performs some operation. #Indent Reduction #Indent +4 Replacing a string of nonterminals and\/or terminals with a single nonterminal, according to a grammar rule. \*Note Algorithm>: The Bison Parser Algorithm . #Indent Reentrant #Indent +4 A reentrant subprogram is a subprogram which can be in invoked any number of times in parallel, without interference between the various invocations. \*Note PureDecl>: A Pure (Reentrant) Parser. #Indent Reverse polish notation #Indent +4 A language in which all operators are postfix operators. #Indent Right recursion #Indent +4 A rule whose result symbol is also its last component symbol; for example, {fEmphasis}expseq1: exp ',' expseq1;{f}. \*Note Recursion>: Recursive Rules. #Indent Semantics #Indent +4 In computer languages, the semantics are specified by the actions taken for each instance of the language, i.e., the meaning of each statement. \*Note Semantics>: Defining Language Semantics. #Indent Shift #Indent +4 A parser is said to shift when it makes the choice of analyzing further input from the stream rather than reducing immediately some already-recognized rule. \*Note Algorithm>: The Bison Parser Algorithm . #Indent Single-character literal #Indent +4 A single character that is recognized and interpreted as is. \*Note GrammarinB>: From Formal Rules to Bison Input. #Indent Start symbol #Indent +4 The nonterminal symbol that stands for a complete valid utterance in the language being parsed. The start symbol is usually listed as the first nonterminal symbol in a language specification. \*Note StartDecl>: The Start-Symbol. #Indent Symbol table #Indent +4 A data structure where symbol names and associated data are stored during parsing to allow for recognition and use of existing information in repeated uses of a symbol. \*Note Multifunct>. #Indent Token #Indent +4 A basic, grammatically indivisible unit of a language. The symbol that describes a token in the grammar is a terminal symbol. The input of the Bison parser is a stream of tokens which comes from the lexical analyzer. \*Note Symbols>. #Indent Terminal symbol #Indent +4 A grammar symbol that has no rules in the grammar and therefore is grammatically indivisible. The piece of text it represents is a token. \*Note Languagean>: Languages and Context-Free Grammars. #Indent