Fixed issue where package doesn't have enough dependencies by adding a lens dependency

.gitignore

@@ -0,0 +1,2 @@
+.stack-work
+*~

ispositive.cabal

@@ -1,6 +1,6 @@
 
 name:               ispositive
-version:            0.1
+version:            0.2
 cabal-version:      >= 1.10
 author:             Christian Dietrich
 maintainer:         Christian Dietrich <[email protected]>
@@ -12,7 +12,7 @@ tested-with:        GHC
 build-type:         Simple
 
 description:
-    Tests whether an Integer is positive.
+    Tests whether a number is a positive integer.
 
 source-repository head
     type:               git
@@ -21,7 +21,17 @@ source-repository head
 library
     build-depends:
         base            >= 4 && < 5
+      , lens
     hs-source-dirs:     src
     default-language:   Haskell2010
     exposed-modules:
         Integer.IsPositive
+
+Test-Suite spec
+  Type:                exitcode-stdio-1.0
+  Default-Language:    Haskell2010
+  Hs-Source-Dirs:      test
+  Main-Is:             Spec.hs
+  Build-Depends:       base >=4 && <5
+                     , hspec
+                     , ispositive

src/Integer/IsPositive.hs

@@ -1,5 +1,17 @@
 module Integer.IsPositive (
    is_positive_integer
+ , is_not_positive_integer
+ , positive_integer_prism
 ) where
 
-is_positive_integer = (0 < )
+import Control.Lens
+import Control.Monad
+
+positive_integer_prism :: RealFrac a => Prism' a a
+positive_integer_prism = prism' id (mfilter p . pure)
+  where
+     p x = 1 <= x && x == fromInteger (floor x)
+
+is_positive_integer = has positive_integer_prism
+
+is_not_positive_integer = hasn't positive_integer_prism

stack.yaml

@@ -0,0 +1,35 @@
+# This file was automatically generated by stack init
+# For more information, see: http://docs.haskellstack.org/en/stable/yaml_configuration.html
+
+# Specifies the GHC version and set of packages available (e.g., lts-3.5, nightly-2015-09-21, ghc-7.10.2)
+resolver: lts-5.9
+
+# Local packages, usually specified by relative directory name
+packages:
+- '.'
+# Packages to be pulled from upstream that are not in the resolver (e.g., acme-missiles-0.3)
+extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+flags: {}
+
+# Extra package databases containing global packages
+extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: >= 1.0.0
+
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor

test/Spec.hs

@@ -0,0 +1,22 @@
+module Main where
+
+import Integer.IsPositive
+import Test.Hspec
+
+main :: IO ()
+main = hspec $ do
+  describe "is_positive_integer" $ do
+    it "-1 is not a positive integer" $
+       is_positive_integer (-1) `shouldBe` False
+
+    it "0 is not a positive integer" $
+       is_positive_integer 0 `shouldBe` False
+
+    it "1 is a positive integer" $
+       is_positive_integer 1 `shouldBe` True
+
+    it "0.01 is not a positive integer" $
+       is_positive_integer 0.01 `shouldBe` False
+
+    it "1.01 is not a positive integer" $
+       is_positive_integer 1.01 `shouldBe` False

test/Spec.hs~

@@ -0,0 +1 @@
+{-# OPTIONS_GHC -F -pgmF hspec-discover #-}