11.6 Local Binding with Splicing Body

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▼ | 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 Taints
11.9 | Expanding Top-Level Forms
11.10 | File Inclusion
11.11 | Syntax Utilities

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

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#### 11.6`` Local Binding with Splicing Body

(require racket/splicing)

The bindings documented in this section are provided by the racket/splicing library, not racket/base or racket.

> syntax splicing-let
> syntax splicing-letrec
> syntax splicing-let-values
> syntax splicing-letrec-values
> syntax splicing-let-syntax
> syntax splicing-letrec-syntax
> syntax splicing-let-syntaxes
> syntax splicing-letrec-syntaxes
> syntax splicing-letrec-syntaxes+values
> syntax splicing-local

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, if a reference to one of the splicing form’s bound variables is evaluated before the variable is initialized, an unbound variable error is raised, instead of the variable evaluating to the undefined value. Also, 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.3: undefined;
> cannot reference undefined identifier

> syntax splicing-syntax-parameterize

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")

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