On this page:
splicing-let
splicing-letrec
splicing-let-values
splicing-letrec-values
splicing-let-syntax
splicing-letrec-syntax
splicing-let-syntaxes
splicing-letrec-syntaxes
splicing-letrec-syntaxes+  values
splicing-local
splicing-syntax-parameterize

12.6 Local Binding with Splicing Body

 (require racket/splicing) package: base
The bindings documented in this section are provided by the racket/splicing library, not racket/base or racket.

Like let, letrec, let-values, letrec-values, let-syntax, letrec-syntax, let-syntaxes, letrec-syntaxes, letrec-syntaxes+values, and local, except that in a definition context, the body forms are spliced into the enclosing definition context (in the same way as for begin).

Examples:

> (splicing-let-syntax ([one (lambda (stx) #'1)])
    (define o one))
> o

1

> one

one: undefined;

 cannot reference undefined identifier

When a splicing binding form occurs in a top-level context or module context, its local bindings are treated similarly to definitions. In particular, syntax bindings are evaluated every time the module is visited, instead of only once during compilation as in let-syntax, etc.

Example:

> (splicing-letrec ([x bad]
                    [bad 1])
    x)

bad.0: undefined;

 cannot reference undefined identifier

If a definition within a splicing form is intended to be local to the splicing body, then the identifier should have a true value for the 'definition-intended-as-local syntax property. For example, splicing-let itself adds the property to locally-bound identifiers as it expands to a sequence of definitions, so that nesting splicing-let within a splicing form works as expected (without any ambiguous bindings).

Like syntax-parameterize, except that in a definition context, the body forms are spliced into the enclosing definition context (in the same way as for begin). In a definition context, the body of splicing-syntax-parameterize can be empty.

Note that require transformers and provide transformers are not affected by syntax parameterization. While all uses of require and provide will be spliced into the enclosing context, derived import or export specifications will expand as if they had not been inside of the splicing-syntax-parameterize.

Examples:

> (define-syntax-parameter place (lambda (stx) #'"Kansas"))
> (define-syntax-rule (where) `(at ,(place)))
> (where)

'(at "Kansas")

> (splicing-syntax-parameterize ([place (lambda (stx) #'"Oz")])
    (define here (where)))
> here

'(at "Oz")