_____
/rispu\
\_____/
,----,._ /
_,-' `---,__,-, /
,' @ `; /
_.' ____ ,_)
.-' `-,....._ `-,
,' ``'''
;
_.-'
(defmacro aif (cond then else)
`(let ((it ,cond))
(if it ,then ,else)))
#lang racket
(require racket/stxparam)
(define-syntax-parameter it (lambda (stx) (raise-syntax-error 'anaphora "missed context" stx)))
(define-syntax-rule (aif cond then else)
(let ([temp cond])
(syntax-parameterize ([it (make-rename-transformer #`temp)])
(if temp then else))))
(define-syntax (aif stx)
(syntax-case stx ()
((~ p t f)
(with-syntax ((it (datum->syntax #f 'it)))
#'(let ((it p))
(if it t f))))))(define-macro (aif p t f)
#:capture it
#'(let ((it p))
(if it t f)))
(define-syntax-case (aif p t f)
(with-literal stx (it) ; stx is unhygienic, contains the called syntax.
#'(let ((it p))
(if it t f))))