Syntax Parameters

usage

(import :std/stxparam)

Macros

defsyntax-parameter

(defsyntax-parameter id default)

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defsyntax-parameter*

(defsyntax-parameter* macro param (errmsg "Bad syntax")) -> macro

  macro  := name of the generated macro
  param  := name of the syntax parameter
  errmsg := custom error message

Expands into a macro with name macro which itself expands into the value of the syntax-parameter param. The optional errmsg can be used to customize syntax error reporting.

Examples:

(defsyntax-parameter* @message @@message "Bad syntax; not in reaction context")

You can now syntax-parameterize a "parent" macro with the @@message parameter. This will allow "children" macros to use the @message macro as a syntax-parameter whose value is bound by the parameterization of @@message. That allows you to pass syntactic information down from a parent macro to its children without using with-syntax in every one of them. The @@message syntax parameter can also be cleanly re-parameterized without affecting existing macros.

See Keeping it Clean with Syntax Parameters and std/actor-v18/message.ss.

syntax-parameterize

(syntax-parameterize ((syntax-parameter value) ...)
  body ...)

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Syntax Bindings

For syntax bindings [phi=+1] for use in macros.