11.9 Expanding Top-Level Forms
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? |
| (expand-once top-level-form) → syntax? |
| top-level-form : any/c |
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? |
| (expand-to-top-form top-level-form) → syntax? |
| top-level-form : any/c |
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? |
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.