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Version: 5.2

34.1 DrRacket Language Levels

Carl Eastlund <cce@racket-lang.org>

 (require unstable/gui/language-level)

This library is unstable; compatibility will not be maintained. See Unstable: May Change Without Warning for more information.

This unit imports drracket:tool^ and exports language-level^.

language-level^ : signature

(make-language-level name 
  mixin ... 
  [#:number number 
  #:hierarchy hierarchy 
  #:summary summary 
  #:url url 
  #:reader reader]) 
  (is-a?/c drracket:language:language<%>)
  name : string?
  path : module-path?
  mixin : (-> class? class?)
  number : integer? = ...
  hierarchy : (listof (cons/c string? integer?)) = ...
  summary : string? = name
  url : (or/c string? #f) = #f
  reader : (->* [] [any/c input-port?] (or/c syntax? eof-object?))
   = read-syntax
Constructs a language level as an instance of drracket:language:language<%> with the given name based on the language defined by the module at path. Applies (drracket:language:get-default-mixin) and the given mixins to simple-language-level% to construct the class, and uses the optional keyword arguments to fill in the language’s description and reader.

(language-level-render-mixin to-sexp 
  (make-mixin-contract drracket:language:language<%>)
  to-sexp : (-> any/c any/c)
  show-void? : boolean?
Produces a mixin that overrides render-value/format to apply to-sexp to each value before printing it, and to skip void? values (pre-transformation) if show-void? is #f.

Produces a mixin that augments capability-value to look up each key in dict, producing the corresponding value if the key is found and deferring to inner otherwise.

Overrides create-executable to print an error message in a dialog box.

Overrides front-end/complete-program to wrap terms from the definition in a module based on the language level’s definition module. This duplicates the behavior of the HtDP teaching languages, for instance.

This mixin enables the macro stepper for its language level.

This mixin overrides on-execute to set up the check-expect test engine to a language level similarly to the HtDP teaching languages.

(language-level-metadata-mixin reader-module 
  (make-mixin-contract drracket:language:language<%>)
  reader-module : module-path?
  meta-lines : exact-nonnegative-integer?
  meta->settings : (-> string? any/c any/c)
  settings->meta : (-> symbol? any/c string?)
This mixin constructs a language level that stores metadata in saved files allowing Drracket to automatically switch back to this language level upon opening them. It overrides get-reader-module, get-metadata, metadata->settings, and get-metadata-lines.

The resulting language level uses the reader from reader-module, and is recognized in files that start with a reader directive for that module path within the first meta-lines lines. Metadata about the language’s settings is marshalled between a string and a usable value (based on a default value) by meta->settings, and between a usable value for a current module (with a symbolic name) by settings->meta.