filter returns a list of each item in the given list for which the given predicate returns a non- #f value.
Keeping this in consideration, what is a pair in racket?
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. Pairs are not mutable (but see Mutable Pairs and Lists). A list is recursively defined: it is either the constant null, or it is a pair whose second value is a list.
Then, why is racket recursion preferred?
Recursion is a favored technique in functional programming because it helps avoid mutation of values.
What is the length of badminton racket?
The length of a badminton racket is measured from the bottom of the racket handle/grip to the tip of the racket head. See illustration above. A typical racket length is between 665m to 675mm, and should not exceed 680mm.
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] …) body …+)
In Racket (and other functional programming languages) lambda s are very useful, when you want to pass an in-line, one-shot function as a parameter without defining it first. For example, suppose that we want to square a list of numbers.
Symbols in The Racket Guide introduces symbols. A symbol is like an immutable string, but symbols are normally interned, so that two symbols with the same character content are normally eq?. All symbols produced by the default reader (see Reading Symbols) are interned.
The append function joins two lists together to make one.
The append function is built into Scheme. It concatenates two lists, that is to say, given two lists list1 and list2 it produces a new list which starts with the same elements as list1 and finishes with those of list2 .
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.