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lambda:
λ:
plambda:
opt-lambda:
popt-lambda:
case-lambda:
pcase-lambda:
let:
plet:
letrec:
let*:
let-values:
letrec-values:
let*-values:
let/  cc:
let/  ec:
define:
struct:
define-struct:
define-struct/  exec:
for:
for*/  and:
for*/  first:
for*/  flvector:
for*/  extflvector:
for*/  fold:
for*/  hash:
for*/  hasheq:
for*/  hasheqv:
for*/  last:
for*/  list:
for*/  lists:
for*/  set:
for*/  or:
for*/  product:
for*/  sum:
for*/  vector:
for*:
for/  and:
for/  first:
for/  flvector:
for/  extflvector:
for/  fold:
for/  hash:
for/  hasheq:
for/  hasheqv:
for/  last:
for/  list:
for/  lists:
for/  set:
for/  or:
for/  product:
for/  sum:
for/  vector:
do:
define-type-alias
define-typed-struct
require/  opaque-type
require-typed-struct
require-typed-struct/  provide
pdefine:
pred
Un
mu
Tuple
Parameter
Pair
values
7.4.0.1

12 Legacy Forms

The following forms are provided by Typed Racket for backwards compatibility.

syntax

(lambda: formals . body)

 
formals = ([v : t] ...)
  | ([v : t] ... v : t *)
  | ([v : t] ... v : t ooo bound)
A function of the formal arguments v, where each formal argument has the associated type. If a rest argument is present, then it has type (Listof t).

syntax

(λ: formals . body)

An alias for the same form using lambda:.

syntax

(plambda: (a ...) formals . body)

(plambda: (a ... b ooo) formals . body)
A polymorphic function, abstracted over the type variables a. The type variables a are bound in both the types of the formal, and in any type expressions in the body.

syntax

(opt-lambda: formals . body)

 
formals = ([v : t] ... [v : t default] ...)
  | ([v : t] ... [v : t default] ... v : t *)
  | ([v : t] ... [v : t default] ... v : t ooo bound)
A function with optional arguments.

syntax

(popt-lambda: (a ...) formals . body)

(popt-lambda: (a ... a ooo) formals . body)
A polymorphic function with optional arguments.

An alias for case-lambda.

syntax

(pcase-lambda: (a ...) [formals body] ...)

(pcase-lambda: (a ... b ooo) [formals body] ...)
A polymorphic function of multiple arities.

syntax

(let: ([v : t e] ...) . body)

(let: loop : t0 ([v : t e] ...) . body)
Local bindings, like let, each with associated types. In the second form, t0 is the type of the result of loop (and thus the result of the entire expression as well as the final expression in body). Type annotations are optional.

Examples:
> (: filter-even : (Listof Natural) (Listof Natural) -> (Listof Natural))
> (define (filter-even lst accum)
    (if (null? lst)
        accum
        (let: ([first : Natural (car lst)]
               [rest  : (Listof Natural) (cdr lst)])
              (if (even? first)
                  (filter-even rest (cons first accum))
                  (filter-even rest accum)))))
> (filter-even (list 1 2 3 4 5 6) null)

- : (Listof Nonnegative-Integer)

'(6 4 2)

Examples:
> (: filter-even-loop : (Listof Natural) -> (Listof Natural))
> (define (filter-even-loop lst)
    (let: loop : (Listof Natural)
          ([accum : (Listof Natural) null]
           [lst   : (Listof Natural) lst])
          (cond
            [(null? lst)       accum]
            [(even? (car lst)) (loop (cons (car lst) accum) (cdr lst))]
            [else              (loop accum (cdr lst))])))
> (filter-even-loop (list 1 2 3 4))

- : (Listof Nonnegative-Integer)

'(4 2)

syntax

(plet: (a ...) ([v : t e] ...) . body)

A polymorphic version of let:, abstracted over the type variables a. The type variables a are bound in both the types of the formal, and in any type expressions in the body. Does not support the looping form of let.

syntax

(letrec: ([v : t e] ...) . body)

syntax

(let*: ([v : t e] ...) . body)

syntax

(let-values: ([([v : t] ...) e] ...) . body)

syntax

(letrec-values: ([([v : t] ...) e] ...) . body)

syntax

(let*-values: ([([v : t] ...) e] ...) . body)

Type-annotated versions of letrec, let*, let-values, letrec-values, and let*-values. As with let:, type annotations are optional.

syntax

(let/cc: v : t . body)

syntax

(let/ec: v : t . body)

Type-annotated versions of let/cc and let/ec. As with let:, the type annotation is optional.

syntax

(define: v : t e)

(define: (a ...) v : t e)
(define: (a ... a ooo) v : t e)
(define: (f . formals) : t . body)
(define: (a ...) (f . formals) : t . body)
(define: (a ... a ooo) (f . formals) : t . body)
These forms define variables, with annotated types. The first form defines v with type t and value e. The second form does the same, but allows the specification of type variables. The third allows for polydotted variables. The fourth, fifth, and sixth forms define a function f with appropriate types. In most cases, use of : is preferred to use of define:.

Examples:
> (define: foo : Integer 10)
> (define: (A) mt-seq : (Sequenceof A) empty-sequence)
> (define: (add [first : Integer]
                [rest  : Integer]) : Integer
    (+ first rest))
> (define: (A) (poly-app [func : (A A -> A)]
                         [first : A]
                         [rest  : A]) : A
    (func first rest))

syntax

struct:

An alias for struct.
An alias for define-struct.
An alias for define-struct/exec.

syntax

for:

An alias for for.
Aliases for the same iteration forms without a :.

syntax

do:

An alias for do.

Equivalent to define-type.
Equivalent to define-struct:
Similar to using the opaque keyword with require/typed.
Similar to using the struct keyword with require/typed.
Similar to require-typed-struct, but also provides the imported identifiers.

syntax

pdefine:

Defines a polymorphic function.

syntax

(pred t)

Equivalent to (Any -> Boolean : t).

syntax

Un

An alias for U.

syntax

mu

An alias for Rec.

syntax

Tuple

An alias for List.

syntax

Parameter

An alias for Parameterof.

syntax

Pair

An alias for Pairof.

syntax

values

An alias for Values.