syntax (struct-lens struct-id field-id)

Returns a lens for viewing the field-id field of a struct-id instance.

Examples:

> (struct foo (a b c) #:transparent) > (lens-view (struct-lens foo a) (foo 1 2 3)) 1 > (lens-set (struct-lens foo a) (foo 1 2 3) 100) (foo 100 2 3)

syntax (define-struct-lenses struct-id)

Given a struct-id, defines a lens for each of its fields.

Examples:

> (struct foo (a b c) #:transparent) > (define-struct-lenses foo) > (lens-view foo-a-lens (foo 1 2 3)) 1 > (lens-set foo-a-lens (foo 1 2 3) 100) (foo 100 2 3)

syntax (struct/lens struct-id (field-spec ...) struct-option ...)

Equivalent to struct and define-struct-lenses combined.

Examples:

> (struct/lens foo (a b c) #:transparent) > (lens-view foo-a-lens (foo 1 2 3)) 1 > (lens-set foo-a-lens (foo 1 2 3) 100) (foo 100 2 3)