 Valuelevel programming

Programming paradigms  Agentoriented
 Automatabased
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 Concurrent computing
 Relativistic programming
 Datadriven
 Declarative (contrast: Imperative)
 Constraint
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 Abductive logic
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 Functionlevel (contrast: Valuelevel)
 Functional
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 Imperative (contrast: Declarative)
 Languageoriented
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 Nonstructured (contrast: Structured)
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 Programming in the large / small
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 Structured (contrast: Nonstructured)
 Modular (contrast: Monolithic)
 Objectoriented
 Recursive
 Valuelevel (contrast: Functionlevel)
Valuelevel programming refers to one of the two contrasting programming paradigms identified by John Backus in his work on Programs as mathematical objects, the other being functionlevel programming. Backus originally used the term objectlevel programming but that term is now prone to confusion with objectoriented programming.
Valuelevel programs are those that describe how to combine various values (i.e., numbers, symbols, strings, etc.) to form other values until the final result values are obtained. New values are constructed from existing ones by the application of various valuetovalue functions, such as addition, concatenation, matrix inversion, and so on.
Conventional, von Neumann programs are valuelevel: expressions on the right side of assignment statements are exclusively concerned with building a value that is then to be stored.
Connection with Data Types
The valuelevel approach to programming invites the study of the space of values under the valueforming operations, and of the algebraic properties of those operations. This is what is called the study of data types, and it has advanced from focusing on the values themselves and their structure, to a primary concern with the valueforming operations and their structure, as given by certain axioms and algebraic laws, that is, to the algebraic study of data types.
Connection with Lambda Calculus languages
Lambda calculusbased languages (such as Lisp, ISWIM, and Scheme) are in actual practice valuelevel languages, although they are not thus restricted by design.
To see why typical lambda style programs are primarily valuelevel, consider the usual definition of a valuetovalue function, say
f = λx.E
here, x must be a value variable (since the argument of f is a value by definition) and E must denote a value too (since f's result is a value by definition). Typically, E is an expression involving the application of valueforming functions to value variables and constants; nevertheless, a few valueforming functions having both function and value arguments do exist and are used for limited purposes.
If the term values is defined to include the value variables themselves, then the valuelevel view of programming is one of building values by the application of existing programs (valueforming operations/functions) to other values. Lambdastyle programming builds a new program from the resultvalue by lambdaabstracting the value variables.
See also
 Functionlevel programming (contrast)
 Programming paradigms
Categories: Programming paradigms
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