Next: Index Prev: Table of Symbols Up: Top
Backus-Naur Form (BNF)
Formal method of specifying context-free grammars. BNF was first
used in the `ALGOL-60' report, 1963. Note: Languages and
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 *anywhere* an
expression is permitted. Note: Languages and Context-Free
Allocation of memory that occurs during execution, rather than at
compile time or on entry to a function.
Analogous to the empty set in set theory, the empty string is a
character string of length zero.
Finite-state stack machine
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: The Bison Parser Algorithm.
A language construct that is (in general) grammatically divisible;
for example, `expression' or `declaration' in C. Note: Languages
and Context-Free Grammars.
An arithmetic operator that is placed between the operands on
which it performs some operation.
A continuous flow of data between devices or programs.
One of the typical usage schemas of the language. For example,
one of the constructs of the C language is the `if' statement.
Note: Languages and Context-Free Grammars.
Operators having left associativity are analyzed from left to
right: `a+b+c' first computes `a+b' and then combines with `c'.
Note: Operator Precedence.
A rule whose result symbol is also its first component symbol; for
example, `expseq1 : expseq1 ',' exp;'. *Note Recursive Rules:
Parsing a sentence of a language by analyzing it token by token
from left to right. Note: The Bison Parser Algorithm.
Lexical analyzer (scanner)
A function that reads an input stream and returns tokens one by
one. Note: The Lexical Analyzer Function `yylex'.
A flag, set by actions in the grammar rules, which alters the way
tokens are parsed. Note: Lexical Tie-ins.
A token already read but not yet shifted. Note: Look-Ahead
The class of context-free grammars that Bison (like most other
parser generators) can handle; a subset of LR(1). *Note
Mysterious Reduce/Reduce Conflicts: Mystery Conflicts.
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
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.
An error encountered during parsing of an input stream due to
invalid syntax. Note: Error Recovery.
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.
An arithmetic operator that is placed after the operands upon
which it performs some operation.
Replacing a string of nonterminals and/or terminals with a single
nonterminal, according to a grammar rule. Note: The Bison Parser
A reentrant subprogram is a subprogram which can be in invoked any
number of times in parallel, without interference between the
various invocations. Note: A Pure (Reentrant) Parser.
Reverse polish notation
A language in which all operators are postfix operators.
A rule whose result symbol is also its last component symbol; for
example, `expseq1: exp ',' expseq1;'. *Note Recursive Rules:
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: Defining Language Semantics.
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 The Bison Parser Algorithm:
A single character that is recognized and interpreted as is.
Note: From Formal Rules to Bison Input.
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: The Start-Symbol.
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: Multi-function
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.
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: Languages and Context-Free Grammars
automatically generated by info2www