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ISWIM
ISWIM (If You See What I Mean) is an abstract computer programming language (or a family of languages) devised by Peter Landin and first described in his article "The Next 700 Programming Languages", published in the ''Communications of the ACM'' in 1966. Although not implemented, it has proved very influential in the development of programming languages, especially functional programming languages such as SASL, Miranda, ML, Haskell and their successors, and dataflow programming languages like Lucid. Design ISWIM is an imperative programming language with a functional core, consisting of a syntactic sugaring of lambda calculus to which are added mutable variables and assignment and a powerful control mechanism: the ''program point'' operator. Being based on lambda calculus, ISWIM has higher-order functions and lexically scoped variables. The operational semantics of ISWIM are defined using Landin's SECD machine and use call-by-value, that is eager evaluation. A goal of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imperative Programming
In computer science, imperative programming is a programming paradigm of software that uses Statement (computer science), statements that change a program's state (computer science), state. In much the same way that the imperative mood in natural languages expresses commands, an imperative program consists of command (computing), commands for the computer to perform. Imperative programming focuses on describing ''how'' a program operates step by step (with general order of the steps being determined in source code by the placement of statements one below the other), rather than on high-level descriptions of its expected results. The term is often used in contrast to declarative programming, which focuses on ''what'' the program should accomplish without specifying all the details of ''how'' the program should achieve the result. Procedural programming Procedural programming is a type of imperative programming in which the program is built from one or more procedures (also termed s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syntactic Sugar
In computer science, syntactic sugar is syntax within a programming language that is designed to make things easier to read or to express. It makes the language "sweeter" for human use: things can be expressed more clearly, more concisely, or in an alternative style that some may prefer. Syntactic sugar is usually a shorthand for a common operation that could also be expressed in an alternate, more verbose, form: The programmer has a choice of whether to use the shorter form or the longer form, but will usually use the shorter form since it is shorter and easier to type and read. For example, many programming languages provide special syntax for referencing and updating array elements. Abstractly, an array reference is a procedure of two arguments: an array and a subscript vector, which could be expressed as get_array(Array, vector(i,j)). Instead, many languages provide syntax such as Array ,j/code>. Similarly an array element update is a procedure consisting of three arguments, fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PAL (programming Language)
PAL, the Pedagogic Algorithmic Language, is a programming language developed at the Massachusetts Institute of Technology in around 1967 to help teach programming language semantics and design.John M. Wozencraft and Arthur Evans, Jr. ''Notes on Programming Linguistics''. Unpublished report, Department of Electrical Engineering, MIT. February, 1971. It is a "direct descendant" of ISWIM and owes much of its philosophy to Christopher Strachey. The initial implementation of PAL, in Lisp, was written by Peter Landin and James H. Morris, Jr. and ran under CTSS. It was later redesigned by Martin Richards, Thomas J. Barkalow, Arthur Evans, Jr., Robert M. Graham, James Morris, and John Wozencraft. It was implemented by Richards and Barkalow in BCPL as an intermediate-code interpreter and ran on the IBM System/360; this was called PAL/360. RPAL RPAL, the Right-reference Pedagogic Algorithmic Language, is a functional subset of PAL with an implementation on SourceForge. It is used at the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Inference
Type inference, sometimes called type reconstruction, refers to the automatic detection of the type of an expression in a formal language. These include programming languages and mathematical type systems, but also natural languages in some branches of computer science and linguistics. Nontechnical explanation In a typed language, a term's type determines the ways it can and cannot be used in that language. For example, consider the English language and terms that could fill in the blank in the phrase "sing _." The term "a song" is of singable type, so it could be placed in the blank to form a meaningful phrase: "sing a song." On the other hand, the term "a friend" does not have the singable type, so "sing a friend" is nonsense. At best it might be metaphor; bending type rules is a feature of poetic language. A term's type can also affect the interpretation of operations involving that term. For instance, "a song" is of composable type, so we interpret it as the thing created ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algebraic Data Type
In computer programming, especially functional programming and type theory, an algebraic data type (ADT) is a kind of composite data type, i.e., a data type formed by combining other types. Two common classes of algebraic types are product types (i.e., tuples, and records) and sum types (i.e., tagged or disjoint unions, coproduct types or ''variant types''). The values of a product type typically contain several values, called ''fields''. All values of that type have the same combination of field types. The set of all possible values of a product type is the set-theoretic product, i.e., the Cartesian product, of the sets of all possible values of its field types. The values of a sum type are typically grouped into several classes, called ''variants''. A value of a variant type is usually created with a quasi-functional entity called a ''constructor''. Each variant has its own constructor, which takes a specified number of arguments with specified types. The set of all po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CPL (programming Language)
CPL (Combined Programming Language) is a multi-paradigm programming language developed in the early 1960s. It is an early ancestor of the C language via the BCPL and B languages. Design CPL was developed initially at the Mathematical Laboratory at the University of Cambridge as the "Cambridge Programming Language" and later published jointly between Cambridge and the University of London Computer Unit as the "Combined Programming Language" (CPL was also nicknamed by some as "Cambridge Plus London" or "Christopher's Programming Language"). Christopher Strachey, David Barron and others were involved in its development. The first paper describing it was published in 1963, while it was being implemented on the Titan Computer at Cambridge and the Atlas Computer at London. It was heavily influenced by ALGOL 60, but instead of being extremely small, elegant and simple, CPL was intended for a wider application area than scientific calculations and was therefore much more complex and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indentation Style
In computer programming, indentation style is a convention or style, governing the indentation of lines of source code. An indentation style generally specifies a consistent number of whitespace characters before each line of a block, so that the lines of code appear to be related, and dictates whether to use spaces or tabs as the indentation character. Overview This article primarily addresses styles for free-form programming languages. As the name implies, such language code need not follow an indentation style. Indentation is a secondary notation that is often intended to lower cognitive load for a programmer to understand the structure of the code. Indentation can clarify the separation between the code executed based on control flow. Structured languages, such as Python and occam, use indentation to determine the structure instead of using braces or keywords; this is termed the off-side rule. In such languages, indentation is meaningful to the language processor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Off-side Rule
The off-side rule describes syntax of a computer programming language that defines the bounds of a code block via indentation. The term was coined by Peter Landin, possibly as a pun on the offside law in association football. An off-side rule language is contrasted with a free-form language in which indentation has no syntactic meaning, and indentation is strictly a matter of style. An off-side rule language is also described as having significant indentation. Definition Peter Landin, in his 1966 article " The Next 700 Programming Languages", defined the off-side rule thus: "Any non-whitespace token to the left of the first such token on the previous line is taken to be the start of a new declaration." Example The following is an example of indentation blocks in Python; a popular off-side rule language. In Python, the rule is taken to define the boundaries of statements rather than declarations. def is_even(a: int) -> bool: if a % 2 0: print('Eve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ALGOL
ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the Association for Computing Machinery (ACM) in textbooks and academic sources for more than thirty years. In the sense that the syntax of most modern languages is "Algol-like", it was arguably more influential than three other high-level programming languages among which it was roughly contemporary: FORTRAN, Lisp, and COBOL. It was designed to avoid some of the perceived problems with FORTRAN and eventually gave rise to many other programming languages, including PL/I, Simula, BCPL, B, Pascal, Ada, and C. ALGOL introduced code blocks and the begin...end pairs for delimiting them. It was also the first language implementing nested function definitions with lexical scope. Moreover, it was the first programming language which gave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eager Evaluation
In a programming language, an evaluation strategy is a set of rules for evaluating expressions. The term is often used to refer to the more specific notion of a ''parameter-passing strategy'' that defines the kind of value that is passed to the function for each parameter (the ''binding strategy'') and whether to evaluate the parameters of a function call, and if so in what order (the ''evaluation order''). The notion of reduction strategy is distinct, although some authors conflate the two terms and the definition of each term is not widely agreed upon. A programming language's evaluation strategy is part of its high-level semantics. Some languages, such as PureScript, have variants with different evaluation strategies. Some declarative languages, such as Datalog, support multiple evaluation strategies. The calling convention consists of the low-level platform-specific details of parameter passing. Example To illustrate, executing a function call f(a,b) may first evaluat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SECD Machine
The SECD machine is a highly influential (see: '' Landin's contribution'') virtual machine and abstract machine intended as a target for compilers of functional programming languages. The letters stand for stack, environment, control, dump, respectively, which are the internal registers of the machine. The registers stack, control, and dump point to (some realizations of) stacks, and environment points to (some realization of) an associative array. The machine was the first to be specifically designed to evaluate lambda calculus expressions. It was originally described by Peter Landin in "The Mechanical Evaluation of Expressions" in 1964. The description published by Landin was fairly abstract, and left many implementation choices open (like an operational semantics). Lispkit Lisp was an influential compiler based on the SECD machine, and the SECD machine has been used as the target for other systems such as Lisp/370. In 1989, researchers at the University of Calgary worked o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lexically Scoped
In computer programming, the scope of a name binding (an association of a name to an entity, such as a variable) is the part of a program where the name binding is valid; that is, where the name can be used to refer to the entity. In other parts of the program, the name may refer to a different entity (it may have a different binding), or to nothing at all (it may be unbound). Scope helps prevent name collisions by allowing the same name to refer to different objects – as long as the names have separate scopes. The scope of a name binding is also known as the visibility of an entity, particularly in older or more technical literature—this is in relation to the referenced entity, not the referencing name. The term "scope" is also used to refer to the set of ''all'' name bindings that are valid within a part of a program or at a given point in a program, which is more correctly referred to as ''context'' or ''environment''. Strictly speaking and in practice for most programmi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
