The list is the fundamental data structure of Racket. A list is a sequence of values. A list can contain any kind of value, including other lists. A list can contain any number of values. If a list has zero values, it’s called the empty list.
Consequently, what is CDR in racket?
Pairs and Lists in The Racket Guide introduces pairs and lists. A pair combines exactly two values. The first value is accessed with the car procedure, and the second value is accessed with the cdr procedure. … A list is recursively defined: it is either the constant null, or it is a pair whose second value is a list.
Additionally, what is a stream in racket?
A stream is a kind of sequence that supports functional iteration via stream-first and stream-rest. … The bindings documented in this section are provided by the racket/stream and racket libraries, but not racket/base.
Why is Racket recursion preferred?
Recursion is a favored technique in functional programming because it helps avoid mutation of values. The first version of our factorial function mutated the variable product on each pass.
What does let do in Racket?
Local Binding: let, let*, letrec, … in The Racket Reference also documents let. A let form binds a set of identifiers, each to the result of some expression, for use in the let body: (let ([id expr] …)
What does CDR do?
The CDR of a list is the rest of the list, that is, the cdr function returns the part of the list that follows the first item. … Like car , cdr does not remove any elements from the list—it just returns a report of what the second and subsequent elements are. Incidentally, in the example, the list of flowers is quoted.
What does car stand for in Lisp?
In computer programming, CAR ( car ) /kɑːr/ ( listen) and CDR ( cdr ) (/ˈkʌdər/ ( listen) or /ˈkʊdər/ ( listen)) are primitive operations on cons cells (or “non-atomic S-expressions”) introduced in the Lisp programming language.
What is null in Scheme?
In Scheme, there is one null pointer value, called “the empty list,” which prints as () . … Conceptually, the empty list is a special object, and a “null” pointer is a pointer to this special end-of-list object.
What is begin in racket?
Begin takes an arbitrary number of expressions and executes each one of them but only returns the result of the last expression in the body. https://stackoverflow.com/questions/29382733/racket-begin-form/29387064#29387064.