Add implementation of SRFI 31.

scheme/more-interfaces.scm

@@ -548,6 +548,9 @@
 	  random-source-make-integers
 	  random-source-make-reals))
 
+(define-interface srfi-31-interface
+  (export (rec :syntax)))
+
 (define-interface srfi-37-interface
   (export
    option

scheme/more-packages.scm

@@ -729,7 +729,7 @@
     (define available-srfis
       '(srfi-1 srfi-2 srfi-5 srfi-6 srfi-7 srfi-8 srfi-9
 	srfi-11 srfi-13 srfi-14 srfi-16 srfi-17 srfi-23
-	srfi-25 srfi-26 srfi-27 srfi-28 srfi-30))
+	srfi-25 srfi-26 srfi-27 srfi-28 srfi-30 srfi-31))
 
     ; Some SRFI's redefine Scheme variables.
     (define shadowed
@@ -854,6 +854,10 @@
 
 ; SRFI-30 - scheme/rts/read.scm contains the reader for #|...|# comments
 
+(define-structure srfi-31 srfi-31-interface
+  (open scheme)
+  (files (srfi srfi-31)))
+
 (define-structure srfi-37 srfi-37-interface
   (open scheme 
 	srfi-9 
@@ -946,7 +950,7 @@
 	    srfi-1 srfi-2 srfi-5 srfi-6 srfi-7 srfi-8 srfi-9
 	    srfi-11 srfi-13 srfi-14 srfi-16 srfi-17
 	    srfi-23 srfi-25 srfi-26 srfi-27 srfi-28
-	    srfi-37
+	    srfi-31 srfi-37
 	    )
 	   :structure)
 	  ((define-signature define-package) :syntax)))

scheme/srfi/srfi-31.scm

@@ -0,0 +1,9 @@
+; Taken directly from the SRFI document.
+
+(define-syntax rec
+  (syntax-rules ()
+    ((rec (NAME . VARIABLES) . BODY)
+     (letrec ( (NAME (lambda VARIABLES . BODY)) ) NAME))
+    ((rec NAME EXPRESSION)
+     (letrec ( (NAME EXPRESSION) ) NAME))))
+