From 7b762933c6eb247b0c8ed11fd59c8b7f18db6c5c Mon Sep 17 00:00:00 2001
From: Eric Dobson <eric.n.dobson@gmail.com>
Date: Wed, 1 Apr 2015 21:36:01 -0700
Subject: [PATCH] Simplify the type of zero?.

---
 .../typed-racket/base-env/base-env-numeric.rkt     |  8 ++------
 typed-racket-test/unit-tests/typecheck-tests.rkt   | 14 +++++++++++++-
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt b/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt
index aa683f59..a93af1df 100644
--- a/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt
+++ b/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt
@@ -891,12 +891,8 @@
 ;; There are 25 values that answer true to zero?. They are either reals, or inexact complexes.
 ;; Note -RealZero contains NaN and zero? returns #f on it
 [zero?
-  (cl->*
-    (-> -ExactNumber B : (-FS (-filter (-val 0) 0) (-not-filter (-val 0) 0)))
-    (-> -Real B : (-FS (-filter -RealZero 0)
-                       (-not-filter (Un -Zero -InexactRealPosZero -InexactRealNegZero) 0)))
-    (-> N B : (-FS (-filter (Un -RealZero -InexactComplex -InexactImaginary) 0)
-                   (-not-filter (Un -Zero -InexactRealPosZero -InexactRealNegZero) 0))))]
+  (-> N B : (-FS (-filter (Un -RealZero -InexactComplex -InexactImaginary) 0)
+                 (-not-filter (Un -Zero -InexactRealPosZero -InexactRealNegZero) 0)))]
 
 [number? (make-pred-ty N)]
 [integer? (asym-pred Univ B (-FS (-filter (Un -Int -Flonum -SingleFlonum) 0) ; inexact-integers exist...
diff --git a/typed-racket-test/unit-tests/typecheck-tests.rkt b/typed-racket-test/unit-tests/typecheck-tests.rkt
index f28765bf..335969fb 100644
--- a/typed-racket-test/unit-tests/typecheck-tests.rkt
+++ b/typed-racket-test/unit-tests/typecheck-tests.rkt
@@ -2058,7 +2058,7 @@
               (-lst -Symbol)]
         [tc-e (sequence-count zero? (inst empty-sequence Integer))
               -Nat]
-        [tc-e (sequence-filter zero? (inst empty-sequence Integer))
+        [tc-e ((inst sequence-filter Integer Zero) zero? (inst empty-sequence Integer))
               (-seq (-val 0))]
         [tc-e (sequence-add-between (inst empty-sequence Integer) 'foo)
               (-seq (t:Un -Int (-val 'foo)))]
@@ -3570,6 +3570,16 @@
        [tc-e/t
          (lambda: ([x : Real-Zero]) (or (zero? x) x))
          (t:-> -RealZero (t:Un (-val #t) -InexactRealNan) : -true-filter)]
+       [tc-e/t
+         (lambda: ([x : Positive-Integer]) (zero? x))
+         (t:-> -PosInt -Boolean : -false-filter)]
+       [tc-e/t
+         (lambda: ([x : Natural]) (zero? x))
+         (t:-> -Nat -Boolean : (-FS (-filter (-val 0) 0) (-not-filter (-val 0) 0)))]
+       [tc-e/t
+         (lambda: ([x : Real]) (zero? x))
+         (t:-> -Real -Boolean : (-FS (-filter -RealZero 0)
+                                     (-not-filter (t:Un -Zero -InexactRealPosZero -InexactRealNegZero) 0)))]
 
        [tc-e/t (lambda: ([x : Byte]) (positive? x))
           (t:-> -Byte -Boolean : (-FS (-filter -PosByte 0) (-filter -Zero 0)))]
@@ -3586,6 +3596,8 @@
        [tc-e/t (lambda: ([x : Flonum]) (or (>= +inf.f x) x))
         (t:-> -Flonum (t:Un (-val #t) -FlonumNan)
               : -true-filter)]
+
+
        )
 
   (test-suite