From 4b2f78477a2f6144044fc2645750f07be923d85d Mon Sep 17 00:00:00 2001
From: Robby Findler <robby@racket-lang.org>
Date: Sun, 19 Feb 2012 08:04:16 -0600
Subject: [PATCH] added nand, nor, and implies to racket/bool

---
 collects/mzlib/etc.rkt                        |  8 ----
 collects/mzlib/scribblings/etc.scrbl          |  4 +-
 collects/racket/bool.rkt                      | 20 +++++++++-
 collects/scribblings/reference/booleans.scrbl | 37 +++++++++++++++++++
 collects/tests/racket/bool.rkt                | 19 ++++++++++
 5 files changed, 77 insertions(+), 11 deletions(-)

diff --git a/collects/mzlib/etc.rkt b/collects/mzlib/etc.rkt
index 7314700272..da40ab976b 100644
--- a/collects/mzlib/etc.rkt
+++ b/collects/mzlib/etc.rkt
@@ -162,14 +162,6 @@
           [(t a ...) (raise-syntax-error #f "invalid clause" stx s)]))
       (syntax->list (syntax (something ...))))]))
 
-(define-syntax (nor stx)
-  (syntax-case stx ()
-    [(_ expr ...) (syntax/loc stx (not (or expr ...)))]))
-
-(define-syntax (nand stx)
-  (syntax-case stx ()
-    [(_ expr ...) (syntax/loc stx (not (and expr ...)))]))
-
 (define-syntax (let+ stx)
   (syntax-case stx ()
     [(_ [clause ...] body1 body ...)
diff --git a/collects/mzlib/scribblings/etc.scrbl b/collects/mzlib/scribblings/etc.scrbl
index c80f9afd1e..3acd10710a 100644
--- a/collects/mzlib/scribblings/etc.scrbl
+++ b/collects/mzlib/scribblings/etc.scrbl
@@ -22,7 +22,7 @@
 
 @mzlib[#:mode title etc]
 
-The @racketmodname[mzlib/etc] library re-exports the following
+The @racketmodname[mzlib/etc] library re-exports the following from
 @racketmodname[scheme/base] and other libraries:
 
 @racketblock[
@@ -35,6 +35,8 @@ The @racketmodname[mzlib/etc] library re-exports the following
   compose
   local
   symbol=?
+  nand 
+  nor
 ]
 
 @defform[(begin-lifted expr ...+)]
diff --git a/collects/racket/bool.rkt b/collects/racket/bool.rkt
index 029c9d209e..6158eb4f7d 100644
--- a/collects/racket/bool.rkt
+++ b/collects/racket/bool.rkt
@@ -1,8 +1,10 @@
-#lang scheme/base
+#lang racket/base
 
 (provide true false false?
          boolean=?
-         symbol=?)
+         symbol=?
+         implies nand nor)
+(require (for-syntax racket/base))
 
 (define true #t)
 (define false #f)
@@ -19,3 +21,17 @@
     (raise-type-error 'symbol=? "symbol" (if (symbol? x) 1 0) x y))
   (eq? x y))
 
+(define-syntax (implies stx)
+  (syntax-case stx ()
+    [(implies x y)
+     (syntax/loc stx (if x y #t))]
+    [(implies x y z w ...)
+     (syntax/loc stx (if x (implies y z w ...) #t))]))
+
+(define-syntax (nor stx)
+  (syntax-case stx ()
+    [(_ expr ...) (syntax/loc stx (not (or expr ...)))]))
+
+(define-syntax (nand stx)
+  (syntax-case stx ()
+    [(_ expr ...) (syntax/loc stx (not (and expr ...)))]))
diff --git a/collects/scribblings/reference/booleans.scrbl b/collects/scribblings/reference/booleans.scrbl
index 08bdc5953d..7d8c78c647 100644
--- a/collects/scribblings/reference/booleans.scrbl
+++ b/collects/scribblings/reference/booleans.scrbl
@@ -1,6 +1,9 @@
 #lang scribble/doc
 @(require "mz.rkt")
 
+@(define bool-eval (make-base-eval))
+@(bool-eval '(require racket/bool))
+
 @title[#:tag "booleans"]{Booleans and Equality}
 
 True and false @deftech{booleans} are represented by the values
@@ -242,3 +245,37 @@ Returns @racket[(equal? a b)] (if @racket[a] and @racket[b] are booleans).}
 
 Returns @racket[(not v)].}
 
+@defform[(nand expr ...)]{
+  Same as @racket[(not (and expr ...))].
+
+  @examples[#:eval 
+            bool-eval
+            (nand #f #t)
+            (nand #f (error 'ack "we don't get here"))]
+}
+
+@defform[(nor expr ...)]{
+  Same as @racket[(not (or expr ...))].
+
+  @examples[#:eval 
+            bool-eval
+            (nor #f #t)
+            (nor #t (error 'ack "we don't get here"))]
+
+          
+}
+
+@defform[(implies expr expr expr ...)]{
+  Checks to be sure that the first
+  expression implies the second, implies
+  the third, etc.
+  
+  @examples[#:eval 
+            bool-eval
+            (implies #f #t)
+            (implies #f #f)
+            (implies #f #f #t)
+            (implies #t #f)
+            (implies #f (error 'ack "we don't get here"))]
+                                       
+}
\ No newline at end of file
diff --git a/collects/tests/racket/bool.rkt b/collects/tests/racket/bool.rkt
index 47970d127e..33c5d6fc74 100644
--- a/collects/tests/racket/bool.rkt
+++ b/collects/tests/racket/bool.rkt
@@ -18,3 +18,22 @@
 (check-false (false? #t))
 (check-false (false? "11"))
 
+(for ([x (in-list '(#f #t))])
+  (for ([y (in-list '(#f #t))])
+    (for ([z (in-list '(#f #t))])
+      (check-equal? (implies x y z)
+                    (or (not x) (or (not y) z))))))
+(check-equal? (implies #f (car 'x)) #t)
+
+
+(check-equal? (nand #f #f) #t)
+(check-equal? (nand #f #t) #t)
+(check-equal? (nand #t #f) #t)
+(check-equal? (nand #t #t) #f)
+(check-equal? (nand #f (car 'x)) #t)
+
+(check-equal? (nor #f #f) #t)
+(check-equal? (nor #t #f) #f)
+(check-equal? (nor #f #t) #f)
+(check-equal? (nor #t #t) #f)
+(check-equal? (nor #t (car 'x)) #f)