Syntax¶

The syntax library (import (syntax)) provides syntax and functions for defining Scheme keywords, more commonly known as macros. In Scheme, macros are hygienic, although there are ways to break hygiene with procedural macros.

define-syntax syntax¶

(define-syntax ⟨keyword⟩ ⟨expression⟩)

The define-syntax form binds a keyword to the result of the evaluated expression which must be a transformer. A transformer is a procedure that takes one argument, a syntax object, and returns another syntax object.

Whenever the keyword is encountered, the expander will pass the syntax into the transformer and replace it with the output.

syntax syntax¶

(syntax ⟨expr⟩)
#'⟨expr⟩

let-syntax and letrec-syntax syntax¶

let-syntax¶

(let-syntax ((⟨keyword⟩ ⟨expr⟩) ...) ⟨body⟩)

letrec-syntax¶

(letrec-syntax ((⟨keyword⟩ ⟨expr⟩) ...) ⟨body⟩)

syntax-rules syntax¶

Hygeinic syntax transformers

syntax-case syntax¶

Low-level syntax transformers

free-identifier=? procedure¶

(free-identifier=? ⟨identifier1⟩ ⟨identifier2⟩)