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As a complementary example, in an expression (e1 (call/cc f)), the continuation for the sub-expression (call/cc f) is (lambda (c) (e1 c)), so the whole expression is equivalent to (f (lambda (c) (e1 c))). In other words it takes a "snapshot" of the current control context or control state of the program as an object and applies f to it.
The key to CPS is to remember that (a) every function takes an extra argument known as its continuation, and (b) every argument in a function call must be either a variable or a lambda expression (not a more complex expression). This has the effect of turning expressions "inside-out" because the innermost parts of the expression must be ...
In a programming language, an evaluation strategy is a set of rules for evaluating expressions. [1] The term is often used to refer to the more specific notion of a parameter-passing strategy [2] that defines the kind of value that is passed to the function for each parameter (the binding strategy) [3] and whether to evaluate the parameters of a function call, and if so in what order (the ...
This is not the desired behavior, as (b) or (c) may have side effects, take a long time to compute, or throw errors. It is usually possible to introduce user-defined lazy control structures in eager languages as functions, though they may depart from the language's syntax for eager evaluation: Often the involved code bodies need to be wrapped ...
The callback technology is implemented differently by programming language. In assembly, C, C++, Pascal, Modula2 and other languages, a callback function is stored internally as a function pointer. Using the same storage allows different languages to directly share callbacks without a design-time or runtime interoperability layer.
This property is inherited from lambda calculus, where multi-argument functions are usually represented in curried form. Currying is related to, but not the same as partial application . [ 1 ] [ 2 ] In practice, the programming technique of closures can be used to perform partial application and a kind of currying, by hiding arguments in an ...
(Here we use the standard notations and conventions of lambda calculus: Y is a function that takes one argument f and returns the entire expression following the first period; the expression . ( ) denotes a function that takes one argument x, thought of as a function, and returns the expression ( ), where ( ) denotes x applied to itself ...
This style of programming is mostly used in functional programming, but it can also be very useful in object-oriented programming. A slightly different interpretation of higher-order programming in the context of object-oriented programming are higher order messages, which let messages have other messages as arguments, rather than functions.