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In computer programming, the lexer hack is a solution to parsing context-sensitive grammars such as C, where classifying a sequence of characters as a variable name or a type name requires contextual information, by feeding contextual information backwards from the parser to the lexer.
[citation needed] Note that the constant is independent of the length of the token, the length of the regular expression and the size of the DFA. However, using the REJECT macro in a scanner with the potential to match extremely long tokens can cause Flex to generate a scanner with non-linear performance. This feature is optional.
A more complex example is the lexer hack in C, where the token class of a sequence of characters cannot be determined until the semantic analysis phase since typedef names and variable names are lexically identical but constitute different token classes. Thus in the hack, the lexer calls the semantic analyzer (say, symbol table) and checks if ...
The alternative tokens allow programmers to use C language bitwise and logical operators which could otherwise be hard to type on some international and non-QWERTY keyboards. The name of the header file they are implemented in refers to the ISO/IEC 646 standard, a 7-bit character set with a number of regional variations, some of which have ...
Common token categories may include identifiers, keywords, separators, operators, literals and comments, although the set of token categories varies in different programming languages. The lexeme syntax is typically a regular language , so a finite state automaton constructed from a regular expression can be used to recognize it.
A snippet of C code which prints "Hello, World!". The syntax of the C programming language is the set of rules governing writing of software in C. It is designed to allow for programs that are extremely terse, have a close relationship with the resulting object code, and yet provide relatively high-level data abstraction.
From July 2009 to December 2012, if you bought shares in companies when James H. Hance, Jr. joined the board, and sold them when he left, you would have a -22.5 percent return on your investment, compared to a 54.5 percent return from the S&P 500.
The PKCS #11 standard defines a platform-independent API to cryptographic tokens, such as hardware security modules (HSM) and smart cards, and names the API itself "Cryptoki" (from "cryptographic token interface" and pronounced as "crypto-key", although "PKCS #11" is often used to refer to the API as well as the standard that defines it).