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Yacc
Yacc (Yet Another Compiler-Compiler) is a computer program for the Unix operating system developed by Stephen C. Johnson. It is a Look Ahead Left-to-Right Rightmost Derivation (LALR) parser generator, generating a LALR parser (the part of a compiler that tries to make syntactic sense of the source code) based on a formal grammar, written in a notation similar to Backus–Naur Form (BNF). Yacc is supplied as a standard utility on BSD and AT&T Unix. GNU-based Linux distributions include Bison, a forward-compatible Yacc replacement. History In the early 1970s, Stephen C. Johnson, a computer scientist at Bell Labs / AT&T, developed Yacc because he wanted to insert an exclusive or operator into a B language compiler (developed using McIlroy's TMG compiler-compiler), but it turned out to be a hard task. As a result, he was directed by his colleague at Bell Labs Al Aho to Donald Knuth's work on LR parsing, which served as the basis for Yacc. Yacc was influenced by and received ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU Bison
GNU Bison, commonly known as Bison, is a parser generator that is part of the GNU Project. Bison reads a specification in the BNF notation (a context-free language), warns about any parsing ambiguities, and generates a parser that reads sequences of tokens and decides whether the sequence conforms to the syntax specified by the grammar. The generated parsers are portable: they do not require any specific compilers. Bison by default generates LALR(1) parsers but it can also generate canonical LR, IELR(1) and GLR parsers. In POSIX mode, Bison is compatible with Yacc, but also has several extensions over this earlier program, including * Generation of counterexamples for conflicts * Location tracking (e.g., file, line, column) * Rich and internationalizable syntax error messages in the generated parsers * Customizable syntax error generation, * Reentrant parsers * Push parsers, with autocompletion * Support for named references * Several types of reports (graphical, XML) on th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LALR Parser Generator
A lookahead LR parser (LALR) generator is a software tool that reads a BNF grammar and creates an LALR parser which is capable of parsing files written in the computer language defined by the BNF grammar. LALR parsers are desirable because they are very fast and small in comparison to other types of parsers. There are other types of parser generators, such as Simple LR parser, LR parser, GLR parser, LL parser and GLL parser generators. What differentiates one from another is the type of BNF grammar which they are capable of accepting and the type of parsing algorithm which is used in the generated parser. An LALR parser generator accepts an LALR grammar as input and generates a parser that uses an LALR parsing algorithm (which is driven by LALR parser tables). In practice, LALR offers a good solution, because LALR(1) grammars are more powerful than SLR(1), and can parse most practical LL(1) grammars. LR(1) grammars are more powerful than LALR(1), but canonical LR(1) parsers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TMG (language)
In computing TMG (TransMoGrifier) is a recursive descent compiler-compiler developed by Robert M. McClure and presented in 1965. TMG ran on systems including OS/360 and early Unix. It was used to build EPL, an early version of PL/I. Douglas McIlroy ported TMG to an early version of Unix. According to Ken Thompson, McIlroy wrote TMG in TMG on a piece of paper and "decided to give his piece of paper his piece of paper," hand-compiling assembly language that he entered and assembled on Thompson's Unix system running on PDP-7. Thompson used TMG in 1970 as a tool to offer Fortran, but due to memory limitations of PDP-7 ended up creating the B programming language which was much influenced by BCPL. The recursive descent algorithm of TMG was studied formally by Alexander Birman and Jeffrey Ullman. The formal description of the algorithms was named ''TMG recognition scheme'' (or simply ''TS''). See also * Top-down parsing language * Yacc Yacc (Yet Another Compiler-Compiler) is a comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Douglas McIlroy
Malcolm Douglas McIlroy (born 1932) is a mathematician, engineer, and programmer. As of 2019 he is an Adjunct Professor of Computer Science at Dartmouth College. McIlroy is best known for having originally proposed Unix pipelines and developed several Unix tools, such as spell, diff, sort, join, graph, speak, and tr. He was also one of the pioneering researchers of macro processors and programming language extensibility. He participated in the design of multiple influential programming languages, particularly PL/I, SNOBOL, ALTRAN, TMG and C++. His seminal work on software componentization and code reuse makes him a pioneer of component-based software engineering and software product line engineering. Biography McIlroy earned his bachelor's degree in engineering physics from Cornell University, and a Ph.D. in applied mathematics from MIT in 1959 for his thesis ''On the Solution of the Differential Equations of Conical Shells'' (advisor Eric Reissner). He taught at MIT from 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compiler
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a low-level programming language (e.g. assembly language, object code, or machine code) to create an executable program. Compilers: Principles, Techniques, and Tools by Alfred V. Aho, Ravi Sethi, Jeffrey D. Ullman - Second Edition, 2007 There are many different types of compilers which produce output in different useful forms. A ''cross-compiler'' produces code for a different CPU or operating system than the one on which the cross-compiler itself runs. A ''bootstrap compiler'' is often a temporary compiler, used for compiling a more permanent or better optimised compiler for a language. Related software include, a program that translates from a low-level language to a h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LALR Parser
In computer science, an LALR parser or Look-Ahead LR parser is a simplified version of a canonical LR parser, to parse a text according to a set of production rules specified by a formal grammar for a computer language. ("LR" means left-to-right, rightmost derivation.) The LALR parser was invented by Frank DeRemer in his 1969 PhD dissertation, ''Practical Translators for LR(k) languages'', in his treatment of the practical difficulties at that time of implementing LR(1) parsers. He showed that the LALR parser has more language recognition power than the LR(0) parser, while requiring the same number of states as the LR(0) parser for a language that can be recognized by both parsers. This makes the LALR parser a memory-efficient alternative to the LR(1) parser for languages that are LALR. It was also proven that there exist LR(1) languages that are not LALR. Despite this weakness, the power of the LALR parser is sufficient for many mainstream computer languages,''LR Parsing: Theory a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AT&T Corporation
AT&T Corporation, originally the American Telephone and Telegraph Company, is the subsidiary of AT&T Inc. that provides voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agencies. During the Bell System's long history, AT&T was at times the world's largest telephone company, the world's largest cable television operator, and a regulated monopoly. At its peak in the 1950s and 1960s, it employed one million people and its revenue ranged between US$3 billion in 1950 ($ in present-day terms) and $12 billion in 1966 ($ in present-day terms). In 2005, AT&T was purchased by Baby Bell and former subsidiary SBC Communications for more than $16 billion ($ in present-day terms). SBC then changed its name to AT&T Inc. Today, AT&T Corporation continues to exist as the long distance subsidiary of AT&T Inc., and its name occasionally shows up in AT&T press releases. Buildings with AT&T logo * AT&T Huro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exclusive Or
Exclusive or or exclusive disjunction is a logical operation that is true if and only if its arguments differ (one is true, the other is false). It is symbolized by the prefix operator J and by the infix operators XOR ( or ), EOR, EXOR, , , , , , and . The negation of XOR is the logical biconditional, which yields true if and only if the two inputs are the same. It gains the name "exclusive or" because the meaning of "or" is ambiguous when both operands are true; the exclusive or operator ''excludes'' that case. This is sometimes thought of as "one or the other but not both". This could be written as "A or B, but not, A and B". Since it is associative, it may be considered to be an ''n''-ary operator which is true if and only if an odd number of arguments are true. That is, ''a'' XOR ''b'' XOR ... may be treated as XOR(''a'',''b'',...). Truth table The truth table of A XOR B shows that it outputs true whenever the inputs differ: Equivalences, elimination, and introduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B (programming Language)
B is a programming language developed at Bell Labs circa 1969 by Ken Thompson and Dennis Ritchie. B was derived from BCPL, and its name may possibly be a contraction of BCPL. Thompson's coworker Dennis Ritchie speculated that the name might be based on Bon, an earlier, but unrelated, programming language that Thompson designed for use on Multics. B was designed for recursive, non-numeric, machine-independent applications, such as system and language software. It was a typeless language, with the only data type being the underlying machine's natural memory word format, whatever that might be. Depending on the context, the word was treated either as an integer or a memory address. As machines with ASCII processing became common, notably the DEC PDP-11 that arrived at Bell, support for character data stuffed in memory words became important. The typeless nature of the language was seen as a disadvantage, which led Thompson and Ritchie to develop an expanded version of the languag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stephen C
Stephen or Steven is a common English first name. It is particularly significant to Christians, as it belonged to Saint Stephen ( grc-gre, Στέφανος ), an early disciple and deacon who, according to the Book of Acts, was stoned to death; he is widely regarded as the first martyr (or "protomartyr") of the Christian Church. In English, Stephen is most commonly pronounced as ' (). The name, in both the forms Stephen and Steven, is often shortened to Steve or Stevie. The spelling as Stephen can also be pronounced which is from the Greek original version, Stephanos. In English, the female version of the name is Stephanie. Many surnames are derived from the first name, including Stephens, Stevens, Stephenson, and Stevenson, all of which mean "Stephen's (son)". In modern times the name has sometimes been given with intentionally non-standard spelling, such as Stevan or Stevon. A common variant of the name used in English is Stephan ; related names that have found some cu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Al Aho
Alfred Vaino Aho (born August 9, 1941) is a Canadian computer scientist best known for his work on programming languages, compilers, and related algorithms, and his textbooks on the art and science of computer programming. Aho was elected into the National Academy of Engineering in 1999 for his contributions to the fields of algorithms and programming tools. He and his long-time collaborator Jeffrey Ullman are the recipients of the 2020 Turing Award, generally recognized as the highest distinction in computer science. Career Aho received a B.A.Sc. (1963) in Engineering Physics from the University of Toronto, then an M.A. (1965) and Ph.D. (1967) in Electrical Engineering/Computer Science from Princeton University. He conducted research at Bell Labs from 1967 to 1991, and again from 1997 to 2002 as Vice President of the Computing Sciences Research Center. Since 1995, he has held the Lawrence Gussman Professorship in Computer Science at Columbia University. He served as chair of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Donald Knuth
Donald Ervin Knuth ( ; born January 10, 1938) is an American computer scientist, mathematician, and professor emeritus at Stanford University. He is the 1974 recipient of the ACM Turing Award, informally considered the Nobel Prize of computer science. Knuth has been called the "father of the analysis of algorithms". He is the author of the multi-volume work ''The Art of Computer Programming'' and contributed to the development of the rigorous analysis of the computational complexity of algorithms and systematized formal mathematical techniques for it. In the process, he also popularized the asymptotic notation. In addition to fundamental contributions in several branches of theoretical computer science, Knuth is the creator of the TeX computer typesetting system, the related METAFONT font definition language and rendering system, and the Computer Modern family of typefaces. As a writer and scholar, Knuth created the WEB and CWEB computer programming systems designed to encou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
