Issue justinethier#203 - Tweaked (real?) to be true if both (zero? (imag-part z)) and (exact? (imag-part z)) are true

Author: justinethier

hs-src/Language/Scheme/Numerical.hs

@@ -479,7 +479,12 @@ numRealPart badArgList = throwError $ NumArgs (Just 1) badArgList
 
 -- |Retrieve imaginary part of a complex number
 numImagPart :: [LispVal] -> ThrowsError LispVal
-numImagPart [(Complex c)] = return $ Float $ imagPart c
+numImagPart [(Complex c)] = do
+  let n = imagPart c
+      f = Float n
+  if isFloatAnInteger f
+     then return $ Number $ floor n
+     else return f
 numImagPart [(Float _)] = return $ Number 0
 numImagPart [(Rational _)] = return $ Number 0
 numImagPart [(Number _)] = return $ Number 0
@@ -594,7 +599,13 @@ isReal :: [LispVal] -> ThrowsError LispVal
 isReal ([Number _]) = return $ Bool True
 isReal ([Rational _]) = return $ Bool True
 isReal ([Float _]) = return $ Bool True
-isReal ([Complex c]) = return $ Bool $ (imagPart c) == 0
+isReal ([Complex c]) = do
+  imagPt <- numImagPart [(Complex c)]
+  isExact <- isNumExact [imagPt]
+  isZero <- numBoolBinopEq [imagPt, (Number 0)]
+  case (isExact, isZero) of
+    (Bool True, Bool True) -> return $ Bool True
+    _ -> return $ Bool False
 isReal _ = return $ Bool False
 
 -- |Predicate to determine if given number is a rational.

tests/t-numerical-ops.scm

@@ -11,8 +11,11 @@
 (assert/equal (complex? 3+4i) #t)
 (assert/equal (complex? 3) #t)
 (assert/equal (real? 3) #t)
-(assert/equal (real? -2.5+0.0i) #t)
+(assert/equal (real? -2.5+0i) #t)
+(assert/equal (real? -2.5+0.1i) #f)
+;(assert/equal (real? -2.5+0.0i) #f)
 ;Issue #14: (assert/equal (real? #e1e103) #t)
+; TODO: (assert/equal (rational? 3.5) #t)
 (assert/equal (rational? 6/10) #t)
 (assert/equal (rational? 6/3) #t)
 (assert/equal (integer? 3+0i) #t)