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Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (including the design and implementation of hardware and software). Computer science is generally considered an area of academic research and distinct from computer programming. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and for preventing security vulnerabilities. Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of repositories o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nominal Sets
Nominal may refer to: Linguistics and grammar * Nominal (linguistics), one of the parts of speech * Nominal, the adjectival form of "noun", as in "nominal agreement" (= "noun agreement") * Nominal sentence, a sentence without a finite verb * Noun phrase or nominal phrase Mathematics * Nominal data, a form of categorical data in statistics * Nominal number, a number used as an identifier in mathematics Titles * Post-nominal letters, letters indicating a title, placed after the name of a person * Pre-nominal letters, letters indicating a title, placed before the name of a person Other uses * Nominal aphasia or anomic aphasia, a problem remembering words and names * Nominal category, a group of objects or ideas that can be collectively grouped on the basis of one or more shared, arbitrary characteristics * Nominal damages, a small award to compensate for technical harm * Nominal GDP, a raw gross domestic product value uncompensated for inflation or deflation * Nominal technique ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abstract Syntax
In computer science, the abstract syntax of data is its structure described as a data type (possibly, but not necessarily, an abstract data type), independent of any particular representation or encoding. This is particularly used in the representation of text in computer languages, which are generally stored in a tree structure as an abstract syntax tree. Abstract syntax, which only consists of the structure of data, is contrasted with concrete syntax, which also includes information about the representation. For example, concrete syntax includes features like parentheses (for grouping) or commas (for lists) which are not included in the abstract syntax, as they are implicit in the structure. Abstract syntaxes are classified as first-order abstract syntax (FOAS), if the structure is abstract but names (identifiers) are still concrete (and thus requires name resolution), and ''higher-order abstract syntax,'' if the names themselves are abstract. Uses To be implemented either for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nominal Terms (computer Science)
Nominal terms are a metalanguage for embedding object languages with binding constructs into. Intuitively, they may be seen as an extension of first-order terms with support for name binding. Consequently, the native notion of equality between two nominal terms is alpha-equivalence (equivalence up to a permutative renaming of bound names). Nominal terms came out of a programme of research into nominal sets, and have a concrete semantics in those sets. Where the regular unification found in Prolog is linear in the size of terms compared, the extension to faithfully capture equivalence of nominal terms, called nominal unification in the literature, is quadratic (Calvès 2013). Based on an earlier PTIME algorithm for nominal unification, alphaProlog is a Prolog-like logic programming language with facilities for binding names in terms, which was intended to be useful for programs acting on program syntax (Cheney 2004). Nominal term embeddings may be seen as alternatives to de B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
De Bruijn Index
In mathematical logic, the De Bruijn index is a tool invented by the Dutch mathematician Nicolaas Govert de Bruijn for representing terms of lambda calculus without naming the bound variables. Terms written using these indices are invariant with respect to α-conversion, so the check for α-equivalence is the same as that for syntactic equality. Each De Bruijn index is a natural number that represents an occurrence of a variable in a λ-term, and denotes the number of binders that are in scope between that occurrence and its corresponding binder. The following are some examples: * The term λ''x''. λ''y''. ''x'', sometimes called the K combinator, is written as λ λ 2 with De Bruijn indices. The binder for the occurrence ''x'' is the second λ in scope. * The term λ''x''. λ''y''. λ''z''. ''x'' ''z'' (''y'' ''z'') (the S combinator), with De Bruijn indices, is λ λ λ 3 1 (2 1). * The term λ''z''. (λ''y''. ''y'' (λ''x''. ''x'')) (λ''x''. ''z'' ''x'') is λ (λ 1 (λ 1) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Higher Order Abstract Syntax
In computer science, higher-order abstract syntax (abbreviated HOAS) is a technique for the representation of abstract syntax trees for languages with variable binders. Relation to first-order abstract syntax An abstract syntax is ''abstract'' because it is represented by mathematical objects that have certain structure by their very nature. For instance, in '' first-order abstract syntax'' (''FOAS'') trees, as commonly used in compilers, the tree structure implies the subexpression relation, meaning that no parentheses are required to disambiguate programs (as they are, in the concrete syntax). HOAS exposes additional structure: the relationship between variables and their binding sites. In FOAS representations, a variable is typically represented with an identifier, with the relation between binding site and use being indicated by using the ''same'' identifier. With HOAS, there is no name for the variable; each use of the variable refers directly to the binding site. There are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
