Merge pull request #85 from dpk/srfi-139

Support SRFI 139

%3a139.sls

@@ -0,0 +1,4 @@
+#!r6rs
+(library (srfi :139)
+  (export define-syntax-parameter syntax-parameterize)
+  (import (srfi :139 impl)))

%3a139/impl.chezscheme.sls

@@ -0,0 +1,31 @@
+(library (srfi :139 impl)
+  (export define-syntax-parameter
+          syntax-parameterize)
+  (import (chezscheme)
+          (srfi :213))
+
+  (define-syntax syntax-parameter? (syntax-rules ()))
+  (define-syntax define-syntax-parameter
+    (syntax-rules ()
+      ((_ name default-transformer)
+       (begin
+         (define-syntax name default-transformer)
+         (define-property name syntax-parameter? #t)))))
+
+  (define-syntax syntax-parameterize
+    (lambda (stx)
+      (capture-lookup
+       (lambda (lookup)
+         (syntax-case stx ()
+           ((_ ((name new-transformer) ...) body_0 body_1 ...)
+            (cond ((find (lambda (n)
+                           (not (lookup n #'syntax-parameter?)))
+                         #'(name ...))
+                   => (lambda (n)
+                        (syntax-violation 'syntax-parameterize
+                                          "identifier is not bound to a syntax parameter"
+                                          stx
+                                          n)))
+                  (else
+                   #'(fluid-let-syntax ((name new-transformer) ...)
+                       body_0 body_1 ...))))))))))