# Kyoto2.org

Tricks and tips for everyone

Operations on numbers Racket uses the same arithmetic operator symbols found in most programming languages: ” + ” for addition, ” – ” for subtraction and negation, ” * ” for multiplication, and ” / ” for division.

### How do you negate numbers in a Racket?

Example: (- 0 12) gets us -12 . Professional Racket will support the shorthand: (- 12) to negate 12 as well.

What is function definition in Racket?

racket Functions Function Definitions Functions in Racket can be created with the lambda form. The form takes a list of arguments and a body. (lambda (x y) (* x y)) In the example above, the function takes in two arguments and returns the result of multiplying them.

What is a special form in Racket?

Typed Racket provides a variety of special forms above and beyond those in Racket. They are used for annotating variables with types, creating new types, and annotating expressions.

## What is empty Racket?

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.

### How do you call a procedure in racket?

You can call a function in Racket by wrapping it in parentheses with the arguments after it. This looks like (function argument …) . Operations like + and * are functions as well, and they use the same syntax as calling f or g .

What is lambda in Racket?

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.

How does begin work in Racket?

The begin form (it’s not a function) just evaluates its subexpressions, and returns the value of the last one. So, if you evaluate (begin 3 4 5) , it will just return 5 . If you evaluate (begin (+ 3 4) (+ 9 1)) , you will get 10 .

## What is pair 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. Pairs are not mutable (but see Mutable Pairs and Lists).

### How does begin work in racket?

What is curry in racket?

racket Higher Order Functions Curry curryr can be used when the arguments need to be inserted at the end. In other words, (curryr list 1 2) will produce a function expecting some new-arguments . When called, that new function will in turn call (list new-arguments 1 2) .

What is CAR and CDR in Scheme?

In Scheme, car , cdr , and cons are the most important functions. The cons function is used to construct pairs and pairs are used to construct the lists. The car and cdr are used to access data and return accordingly first and second element from a pair.

## What does CDR return?

After car has been applied to a list, the list is still the same as it was. In the jargon, car is `non-destructive’. This feature turns out to be important. 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.

### What is a pair in racket?

What does cons do in Scheme?

What do CAR and CDR do in Scheme?