6.9 Comprehensions and Sequences

syntax
( for/array: maybe-shapemaybe-fill(for:-clause...)maybe-type-ann
body...+)

syntax
( for*/array: maybe-shapemaybe-fill(for:-clause...)maybe-type-ann
body...+)

maybe-shape =
| #:shapeds

maybe-fill =
| #:fillfill

maybe-type-ann =
| :body-type

ds : In-Indexes
fill : body-type

Creates arrays by generating elements in a for -loop or for* -loop. Unlike other Typed Racket loop macros, these accept a body annotation, which declares the type of elements. They do not accept an annotation for the entire type of the result.

Examples:

> (for/array: ([x(in-range 3)][y(in-range 3)]):Integer
(+ xy))

- : #(struct:Mutable-Array

(Indexes

Index

(Boxof Boolean)

(-> Void)

(-> Indexes Integer)

(-> Indexes Integer Void)

(Vectorof Integer))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-mutable-array.rkt:14:13 prop:custom-write>)

(mutable-array #[0 2 4])

> (for*/array: ([x(in-range 3)][y(in-range 3)]):Integer
(+ xy))

- : #(struct:Mutable-Array

(Indexes

Index

(Boxof Boolean)

(-> Void)

(-> Indexes Integer)

(-> Indexes Integer Void)

(Vectorof Integer))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-mutable-array.rkt:14:13 prop:custom-write>)

(mutable-array #[0 1 2 1 2 3 2 3 4])

The shape of the result is independent of the loop clauses: note that the last example does not have shape #(33), but shape #(9). To control the shape, use the #:shape keyword:

> (for*/array: #:shape#(33)([x(in-range 3)]
[y(in-range 3)]):Integer
(+ xy))

- : #(struct:Mutable-Array

(Indexes

Index

(Boxof Boolean)

(-> Void)

(-> Indexes Integer)

(-> Indexes Integer Void)

(Vectorof Integer))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-mutable-array.rkt:14:13 prop:custom-write>)

(mutable-array #[#[0 1 2] #[1 2 3] #[2 3 4]])

If the loop does not generate enough elements, the rest are filled with the first generated value:

> (for*/array: #:shape#(4)([x(in-range 13)])x)

- : #(struct:Mutable-Array

(Indexes

Index

(Boxof Boolean)

(-> Void)

(-> Indexes Any)

(-> Indexes Any Void)

(Vectorof Any))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-mutable-array.rkt:14:13 prop:custom-write>)

(mutable-array #[1 2 1 1])

To change this behavior, use the #:fill keyword:

> (for*/array: #:shape#(4)#:fill-1([x(in-range 13)])x)

- : #(struct:Mutable-Array

(Indexes

Index

(Boxof Boolean)

(-> Void)

(-> Indexes Any)

(-> Indexes Any Void)

(Vectorof Any))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-mutable-array.rkt:14:13 prop:custom-write>)

(mutable-array #[1 2 -1 -1])

In the last two examples, the array’s type is (Mutable-Array Any ) because a body annotation was not given.

syntax
( for/array maybe-shapemaybe-fill(for-clause...)
body...+)

syntax
( for*/array maybe-shapemaybe-fill(for-clause...)
body...+)

Untyped versions of the loop macros.

procedure
( in-array arr)→(Sequenceof A)
arr:(Array A)

Returns a sequence of arr’s elements in row-major order.

Examples:

> (define arr(array #[#[12]#[1020]]))
> (for/list:: (Listof Integer )([x(in-array arr)])x)

- : (Listof Integer)

'(1 2 10 20)

procedure
( in-array-axis arr[axis])→(Sequenceof (Array A))
arr:(Array A)
axis:Integer =0

Like array->array-list , but returns a sequence.

Examples:

> (define arr(array #[#[12]#[1020]]))
> (sequence->list(in-array-axis arr))

- : (Listof

#(struct:Array

(Indexes Index (Boxof Boolean) (-> Void) (-> Indexes Positive-Byte))

#<syntax:.../array/typed-array-struct.rkt:56:13 prop:equal+hash>

#<syntax:.../array/typed-array-struct.rkt:55:13 prop:custom-write>

#<syntax:.../array/typed-array-struct.rkt:54:13 prop:custom-print-quotable>))

(list (array #[1 2]) (array #[10 20]))
> (sequence->list(in-array-axis arr1))

- : (Listof

#(struct:Array

(Indexes Index (Boxof Boolean) (-> Void) (-> Indexes Positive-Byte))

#<syntax:.../array/typed-array-struct.rkt:56:13 prop:equal+hash>

#<syntax:.../array/typed-array-struct.rkt:55:13 prop:custom-write>

#<syntax:.../array/typed-array-struct.rkt:54:13 prop:custom-print-quotable>))

(list (array #[1 10]) (array #[2 20]))

procedure
( in-array-indexes ds)→(Sequenceof Indexes )
ds:In-Indexes

Returns a sequence of indexes for shape ds, in row-major order.

Examples:

> (for/array: #:shape#(33)([js(in-array-indexes #(33))]): Indexes
js)

- : #(struct:Mutable-Array

(Indexes

Index

(Boxof Boolean)

(-> Void)

(-> Indexes Indexes)

(-> Indexes Indexes Void)

(Vectorof Indexes))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-mutable-array.rkt:14:13 prop:custom-write>)

(mutable-array

#[#['#(0 0) '#(0 1) '#(0 2)]

#['#(1 0) '#(1 1) '#(1 2)]

#['#(2 0) '#(2 1) '#(2 2)]])

> (for*/array: #:shape#(33)([j0(in-range 3)]
[j1(in-range 3)]): In-Indexes
(vector j0j1))

- : #(struct:Mutable-Array

(Indexes

Index

(Boxof Boolean)

(-> Void)

(-> Indexes In-Indexes)

(-> Indexes In-Indexes Void)

(Vectorof In-Indexes))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-mutable-array.rkt:14:13 prop:custom-write>)

(mutable-array

#[#['#(0 0) '#(0 1) '#(0 2)]

#['#(1 0) '#(1 1) '#(1 2)]

#['#(2 0) '#(2 1) '#(2 2)]])
> (indexes-array #(33))

- : #(struct:Array

(Indexes Index (Boxof Boolean) (-> Void) (-> Indexes Indexes))

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-array-struct.rkt:56:13 prop:equal+hash>

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-array-struct.rkt:55:13 prop:custom-write>

#<syntax:build/user/8.18/pkgs/math-lib/math/private/array/typed-array-struct.rkt:54:13 prop:custom-print-quotable>)

(array

#[#['#(0 0) '#(0 1) '#(0 2)]

#['#(1 0) '#(1 1) '#(1 2)]

#['#(2 0) '#(2 1) '#(2 2)]])

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