Initial data commit

Task/Enumerations/Scheme/enumerations-1.ss

@@ -0,0 +1,8 @@
+(define apple 0)
+(define banana 1)
+(define cherry 2)
+
+(define (fruit? atom)
+  (or (equal? 'apple atom)
+      (equal? 'banana atom)
+      (equal? 'cherry atom)))

Task/Enumerations/Scheme/enumerations-2.ss

@@ -0,0 +1,40 @@
+; Syntax that implements a C-like enum; items without assignment take next value.
+; Form: (enum <name> <item>...)
+; Where <name> is a symbol that will be the name of the enum; <item> are one or
+; more expressions that are either symbols or lists of symbol and integer value.
+; The symbols are bound to the values.  If a value is not given, then the next
+; integer after the one bound to the previous symbol is used (starting at 0).
+; The <name> itself is bound to an a-list of the item symbols and their values.
+
+(define-syntax enum
+  (lambda (x)
+    (syntax-case x ()
+      ((_ name itm1 itm2 ...)
+        (identifier? (syntax name))
+        (syntax
+          (begin
+            (define name '())
+            (enum-help name 0 itm1 itm2 ...)))))))
+
+; Helper for (enum) syntax, above.  Do not call directly!
+
+(define-syntax enum-help
+  (lambda (x)
+    (syntax-case x ()
+      ((_ name nxint)
+        (syntax (void)))
+      ((_ name nxint (sym val) rest ...)
+        (and (identifier? (syntax sym))
+             (integer? (syntax-object->datum (syntax val))))
+        (syntax
+          (begin
+            (define sym val)
+            (set! name (cons (cons 'sym val) name))
+            (enum-help name (1+ val) rest ...))))
+      ((_ name nxint sym rest ...)
+        (identifier? (syntax sym))
+        (syntax
+          (begin
+            (define sym nxint)
+            (set! name (cons (cons 'sym nxint) name))
+            (enum-help name (1+ nxint) rest ...)))))))

Task/Enumerations/Scheme/enumerations-3.ss

@@ -0,0 +1,28 @@
+(define-syntax test
+  (syntax-rules ()
+    ((_ e)
+      (printf "~a --> ~s~%" 'e e))))
+
+(printf "~%The 'foo' enum:~%")
+
+(enum foo a (b 10) c (d 20) e (f 30) g)
+
+(test a)
+(test b)
+(test c)
+(test d)
+(test e)
+(test f)
+(test g)
+(test foo)
+(test (assq 'd foo))
+(test (assq 'm foo))
+
+(printf "~%The 'bar' enum:~%")
+
+(enum bar x y (z 99))
+
+(test x)
+(test y)
+(test z)
+(test bar)