From 8b762275c08c966fc74ca05127741e4927349c45 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Georges=20Dup=C3=A9ron?= <georges.duperon@gmail.com>
Date: Thu, 1 Jun 2017 16:43:31 +0200
Subject: [PATCH] First draft to allow #'x and #,x for matching as syntax
 variable or executing syntax-e, respectively, in the % form.

---
 percent2.rkt           | 106 +++++++++++++++++++++++++++++++++++++++++
 test/test-percent2.rkt |   7 +++
 2 files changed, 113 insertions(+)
 create mode 100644 percent2.rkt
 create mode 100644 test/test-percent2.rkt

diff --git a/percent2.rkt b/percent2.rkt
new file mode 100644
index 0000000..f53ee94
--- /dev/null
+++ b/percent2.rkt
@@ -0,0 +1,106 @@
+#lang typed/racket
+(require "typed-untyped.rkt")
+(define-typed/untyped-modules #:no-test
+  (provide % define% in let1)
+
+  (require (for-syntax syntax/parse
+                       "typed-untyped.rkt")
+           "in.rkt")
+  (begin-for-syntax
+    (if-typed (require phc-toolkit/aliases)
+              (require phc-toolkit/untyped/aliases)))
+
+  (define-syntax-rule (let1 var val . body)
+    (let-values ([(var) val]) . body))
+  
+  #|(define-syntax (% stx)
+  (syntax-parse stx #:literals (= → :)
+    [(_ (~seq (~or ((~and var (~not :)) ...)
+                   (~seq (~and var (~not (~or = → :))) ...)) = expr)
+        ...
+        (~optional (~literal →)) . body)
+     #'(let-values ([(var ...) expr] ...) . body)]))|#
+
+  (define-for-syntax mymatch
+    (syntax-parser
+      #:literals (cons list vector syntax)
+      ;; TODO: use define/with-syntax if we are in syntax mode.
+      [(_ val (v:id)) #'(define v val)]
+      [(_ val (cons a b)) #'(begin (mymatch (car val) a)
+                                   (mymatch (car val) b))]
+      [(_ val null)
+       #'(assert val null?)]
+      ;; TODO: handle ellipses
+      [(_ val (list pat ...))
+       #'(mymatch val (list* pat ... null))]
+      [(_ val (list* pat ... rest-pat))
+       #:with (tmp* ...) (generate-temporaries #'(list pat ...))
+       #:with (tmp ... _) #'(tmp* ...)
+       #:with (_ new-tmp ...) #'(tmp* ...)
+       #:with (first . _) #'(tmp* ...)
+       #:with (_ ... last) #'(tmp* ...)
+       #'(begin
+           (define first val)
+           (begin (mymatch (car tmp) pat)
+                  (define new-tmp (cdr tmp)))
+           ...
+           (mymatch last rest-pat))]))
+  
+  (begin-for-syntax
+    (define-syntax-class %pat
+      (pattern v:id
+               #:with expanded #'v)
+      (pattern ()
+               #:with expanded #'(list))
+      (pattern ({~literal unsyntax} x:%pat)
+               #:with expanded #'(app syntax-e x.expanded))
+      (pattern (x:%pat . rest:%pat)
+               #:with expanded #'(cons x.expanded rest.expanded))
+      (pattern #(x:%pat …)
+               #:with expanded #'(vector x.expanded …)))
+    (define-splicing-syntax-class %assignment
+      #:attributes ([pat.expanded 1] [expr 0])
+      #:literals (= in)
+      (pattern (~seq (~and maybe-pat (~not (~or = in))) ...
+                     (~datum =) expr:expr)
+               #:with [pat:%pat ...] #'(maybe-pat ...))))
+  
+  (define-syntax (% stx)
+    (syntax-parse stx #:literals (= in)
+      [(_ :%assignment ... (~optional (~literal in)) . body)
+       #'(match-let*-values ([(pat.expanded ...) expr] ...)
+                            . body)]))
+  
+  (begin-for-syntax
+    (define-syntax-class typed-pat
+      (pattern [x:%pat (~literal :) type:expr]
+               #:with (tmp) (generate-temporaries #'(x))
+               #:with var-type #`[tmp : type]
+               #:with (expanded ...) #'([x.expanded tmp]))
+      (pattern x:id
+               #:with var-type #'x
+               #:with (expanded ...) #'())
+      (pattern x:%pat
+               #:with (tmp) (generate-temporaries #'(x))
+               #:with var-type #'tmp
+               #:with (expanded ...) #'([x.expanded tmp]))))
+  
+  (define-syntax (define% stx)
+    (syntax-parse stx
+      [(_ (name param:typed-pat ...)
+          (~and (~seq ret ...) (~optional (~seq (~literal :) ret-type)))
+          . body)
+       #'(define (name param.var-type ...)
+           (match-let (param.expanded ... ...) ret ... . body))]))
+  
+  #|
+  (begin-for-syntax
+    (define-syntax-class λ%expr
+      (pattern e:id #:where (symbol->string e))
+      (pattern e)
+      (pattern (e . rest:λ%expr))))
+  
+  (define-syntax (λ% stx)
+    (syntax-parse stx
+      [(_ expr )]))
+  |#)
\ No newline at end of file
diff --git a/test/test-percent2.rkt b/test/test-percent2.rkt
new file mode 100644
index 0000000..1fa209b
--- /dev/null
+++ b/test/test-percent2.rkt
@@ -0,0 +1,7 @@
+#lang typed/racket
+(require phc-toolkit/percent2
+         typed/rackunit)
+(check-equal? (% #,x = #'y
+                 in
+                 x)
+              'y)
\ No newline at end of file