StructureIntroduction - Cookbook - s c h e m a t i c s : c o o k b o o k

Introduction

Structures are the built in records in PLT. A stucture type is a record datatype with a number of fields. A structure is an instance of a given structure type. Structures are first class values that contain a value for each field of the the structure type.

;; Small usage example

> (define-struct user (name password))
> (define guest (make-user "Anonymous" "1234")
> (user? guest)
#t
> (user-name guest)
"Anonymous"
> (set-user-name! guest "Guest")
> (user-name guest)
"Guest"

If you want to use records portable across implementations, have a look at SRFI9.

The equivalent record declaration in SRFI-9 would be:

; egregiously PLT-specific module syntax
> (require (lib "9.ss" "srfi"))
> (define-record-type :user
      (make-user name password)
      user?
      (name user-name set-user-name!)
      (password user-password set-user-password!))
> (define guest (make-user "Anonymous" "1234"))
> (user? guest)
#t
> (user-name guest)
"Anonymous"
> (set-user-name! guest "Guest")
> (user-name guest)
"Guest"

-- JensAxelSoegaard - 04 Jun 2004 -- GordonWeakliem - 02 Sep 2004

CookbookForm
TopicType:	Section
ParentTopic:	StructureChapter
TopicOrder:	010

Current Rev: r1.2 - 10 Oct 2004 - 08:30 GMT - JensAxelSoegaard, Revision History:Diffs | r1.3 | > | r1.2 | > | r1.1

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