Move syntax definitions to a new file

This commit is contained in:
Cadence Ember 2022-09-11 19:38:20 +12:00
parent e4bc962b05
commit 4ad22ca9c1
Signed by untrusted user: cadence
GPG key ID: BC1C2C61CF521B17
2 changed files with 56 additions and 24 deletions

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@ -1,5 +1,6 @@
#lang racket/base
(require (for-syntax racket/base)
(require "syntax.rkt"
(for-syntax racket/base)
racket/string
net/url
(prefix-in host: web-server/dispatchers/dispatch-host)
@ -15,29 +16,6 @@
; procedure to make the tree from the hashmap
make-dispatcher-tree)
(define-syntax (if/out stx)
(define tree (cdr (syntax->datum stx))) ; condition true false
(define else (cddr tree)) ; the else branch cons cell
(define result
(let walk ([node tree])
(cond
; normally, node should be a full cons cell (a pair) but it might be something else.
; situation: reached the end of a list, empty cons cell
[(null? node) node]
; situation: reached the end of a list, cons cdr was non-list
[(symbol? node) node]
; normal situation, full cons cell
; -- don't go replacing through nested if/out
[(and (pair? node) (eq? 'if/out (car node))) node]
; -- replace if/in
[(and (pair? node) (eq? 'if/in (car node)))
(append '(if) (cdr node) else)]
; recurse down pair head and tail
[(pair? node) (cons (walk (car node)) (walk (cdr node)))]
; something else that can't be recursed into, so pass it through
[#t node])))
(datum->syntax stx (cons 'if result)))
; make a hashmap out of the provided names and call make-dispatcher-tree with it
(define-syntax (dispatcher-tree stx)
; the arguments, which are names of dispatcher variables

54
src/syntax.rkt Normal file
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@ -0,0 +1,54 @@
#lang racket/base
(require (for-syntax racket/base))
(provide
; help make a nested if where the false results are the same
if/out)
(module+ test
(require rackunit)
(define (check-syntax-equal? s1 s2)
(check-equal? (syntax->datum s1)
(syntax->datum s2))))
;; actual transforming goes on in here.
;; it's in a submodule so that it can be required in both levels, for testing
(module transform racket/base
(provide transform-if/out)
(define (transform-if/out stx)
(define tree (cdr (syntax->datum stx))) ; condition true false
(define else (cddr tree)) ; the else branch cons cell
(define result
(let walk ([node tree])
(cond
; normally, node should be a full cons cell (a pair) but it might be something else.
; situation: reached the end of a list, empty cons cell
[(null? node) node]
; situation: reached the end of a list, cons cdr was non-list
[(symbol? node) node]
; normal situation, full cons cell
; -- don't go replacing through nested if/out
[(and (pair? node) (eq? 'if/out (car node))) node]
; -- replace if/in
[(and (pair? node) (eq? 'if/in (car node)))
(append '(if) (cdr node) else)]
; recurse down pair head and tail
[(pair? node) (cons (walk (car node)) (walk (cdr node)))]
; something else that can't be recursed into, so pass it through
[#t node])))
(datum->syntax stx (cons 'if result))))
;; the syntax definitions and their tests go below here
(require 'transform (for-syntax 'transform))
(define-syntax (if/out stx)
(transform-if/out stx))
(module+ test
(check-syntax-equal? (transform-if/out #'(if/out (condition 1) (if/in (condition 2) (do-yes)) (do-no)))
#'(if (condition 1) (if (condition 2) (do-yes) (do-no)) (do-no)))
(check-equal? (if/out #t (if/in #t 'yes) 'no) 'yes)
(check-equal? (if/out #f (if/in #t 'yes) 'no) 'no)
(check-equal? (if/out #t (if/in #f 'yes) 'no) 'no)
(check-equal? (if/out #f (if/in #f 'yes) 'no) 'no))