11.9 Expanding Top-Level Forms

► |  | Reference: Racket

1 | Language Model
2 | Syntactic Forms
3 | Datatypes
4 | Structures
5 | Classes and Objects
6 | Units
7 | Contracts
8 | Pattern Matching
9 | Control Flow
10 | Concurrency
11 | Macros
12 | Input and Output
13 | Reflection and Security
14 | Operating System
15 | Memory Management
16 | Unsafe Operations
17 | Running Racket
| Bibliography
| Index

▼ | 11 | Macros

11.1 | Pattern-Based Syntax Matching
11.2 | Syntax Object Content
11.3 | Syntax Object Bindings
11.4 | Syntax Transformers
11.5 | Syntax Parameters
11.6 | Local Binding with Splicing Body
11.7 | Syntax Object Properties
11.8 | Syntax Certificates
11.9 | Expanding Top-Level Forms
11.10 | File Inclusion

► | 11.9 | Expanding Top-Level Forms

11.9.1 | Information on Expanded Modules

On this page:

expand
expand-syntax
expand-once
expand-syntax-once
expand-to-top-form
expand-syntax-to-top-form
11.9.1`` Information on Expanded Modules

top← prev up next →

#### 11.9`` Expanding Top-Level Forms

( expand top-level-form) → syntax?
top-level-form : any/c

Expands all non-primitive syntax in top-level-form, and returns a syntax object for the expanded form that contains only core forms, matching the grammar specified by Fully Expanded Programs.

Before top-level-form is expanded, its lexical context is enriched with namespace-syntax-introduce, just as for eval. Use syntax->datum to convert the returned syntax object into a printable datum.

Here’s an example of using expand on a module:

( parameterize ([ current-namespace ( make-base-namespace)])
( expand
( datum->syntax
#f
'(module foo scheme
(define a 3)
(+ a 4)))))

Here’s an example of using expand on a non-top-level form:

( define-namespace-anchor anchor)
( parameterize ([ current-namespace
( namespace-anchor->namespace anchor)])
( expand
( datum->syntax
#f
'(delay (+ 1 2)))))

( expand-syntax stx) → syntax?
stx : syntax?

Like ( expand stx), except that the argument must be a syntax object, and its lexical context is not enriched before expansion.

( expand-once top-level-form) → syntax?
top-level-form : any/c

Partially expands form-level-form and returns a syntax object for the partially-expanded expression. Due to limitations in the expansion mechanism, some context information may be lost. In particular, calling expand-once on the result may produce a result that is different from expansion via expand.

Before top-level-form is expanded, its lexical context is enriched with namespace-syntax-introduce, as for eval.

( expand-syntax-once stx) → syntax?
stx : syntax?

Like ( expand-once stx), except that the argument must be a syntax object, and its lexical context is not enriched before expansion.

( expand-to-top-form top-level-form) → syntax?
top-level-form : any/c

Partially expands top-level-form to reveal the outermost syntactic form. This partial expansion is mainly useful for detecting top-level uses of begin. Unlike the result of expand-once, expanding the result of expand-to-top-form with expand produces the same result as using expand on the original syntax.

Before stx-or-sexpr is expanded, its lexical context is enriched with namespace-syntax-introduce, as for eval.

( expand-syntax-to-top-form stx) → syntax?
stx : syntax?

Like ( expand-to-top-form stx), except that the argument must be a syntax object, and its lexical context is not enriched before expansion.

##### 11.9.1`` Information on Expanded Modules

Information for an expanded module declaration is stored in a set of syntax properties (see Syntax Object Properties) attached to the syntax object:

- 'module-direct-requires – a list of module path indexes (or symbols) representing the modules explicitly imported into the module.

- 'module-direct-for-syntax-requires – a list of module path indexes (or symbols) representing the modules explicitly for-syntax imported into the module.

- 'module-direct-for-template-requires – a list of module path indexes (or symbols) representing the modules explicitly for-template imported into the module.

- 'module-variable-provides – a list of provided items, where each item is one of the following:

  - symbol – represents a locally defined variable that is provided with its defined name.

  - ( cons provided-sym defined-sym) – represents a locally defined variable that is provided with renaming; the first symbol is the exported name, and the second symbol is the defined name.

  - ( list* module-path-index provided-sym defined-sym) – represents a re-exported and possibly re-named variable from the specified module; module-path-index is either a module path index or symbol (see Compiled Modules and References), indicating the source module for the binding. The provided-sym is the external name for the re-export, and defined-sym is the originally defined name in the module specified by module-path-index.

- 'module-syntax-provides – like 'module-variable-provides, but for syntax exports instead of variable exports.

- 'module-indirect-provides – a list of symbols for variables that are defined in the module but not exported; they may be exported indirectly through macro expansions. Definitions of macro-generated identifiers create uninterned symbols in this list.

top← prev up next →