What does cdr mean in Scheme?

What does cdr mean in Scheme?

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 are car and CDR used for?

The car and cdr functions are used for splitting lists and are considered fundamental to Lisp. Since they cannot split or gain access to the parts of an array, an array is considered an atom. Conversely, the other fundamental function, cons , can put together or construct a list, but not an array.

What is CADR in Scheme?

car = first item cdr = second and all subsequent items in list cadr = second item. Cdr. Similar to the car primitive, cdr refers to the phrase “Contents of Decrement part of Register.” On the original hardware, this referred to the second and subsequent items in a list.

What does CDDR do in Scheme?

The two most important ones are cadr and cddr . cadr takes the car of the cdr , which gives you the second item in the list. cddr takes the cdr of the cdr , skipping the first two pairs in a list and returning the rest of the list.

Why are cars called cdr?

The origins of the names for car and cdr are a little bit historical and comes from the IBM 704. car is an acronym from the phrase Contents of the Address part of the Register; and cdr is an acronym from the phrase Contents of the Decrement part of the Register.

Is Scheme a Lisp?

Scheme is a statically scoped and properly tail-recursive dialect of the Lisp programming language invented by Guy Lewis Steele Jr. and Gerald Jay Sussman. It was designed to have an exceptionally clear and simple semantics and few different ways to form expressions.

How do I use append in Scheme?

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 .

What is pair in Scheme?

Pairs are used to combine two Scheme objects into one compound object. Hence the name: A pair stores a pair of objects. The data type pair is extremely important in Scheme, just like in any other Lisp dialect.

What is a pair in Scheme?

What is map in Scheme?

Map is a built in Scheme function that takes a function and a list as an argument, and returns the list that results by applying that function to every element of the list.