Add getErrorOr

Matches Haskell's Either.fromRight

src/main/kotlin/com/mikebull94/result/Get.kt

@@ -23,6 +23,7 @@ fun <V, E> Result<V, E>.getError(): E? {
 
 /**
  * - Elm: [Result.withDefault](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#withDefault)
+ * - Haskell: [Result.fromLeft](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Either.html#v:fromLeft)
  * - Rust: [Result.unwrap_or](https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap_or)
  */
 infix fun <V, E> Result<V, E>.getOr(default: V): V {
@@ -32,6 +33,16 @@ infix fun <V, E> Result<V, E>.getOr(default: V): V {
     }
 }
 
+/**
+ * - Haskell: [Result.fromRight](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Either.html#v:fromRight)
+ */
+infix fun <V, E> Result<V, E>.getErrorOr(default: E): E {
+    return when (this) {
+        is Ok -> default
+        is Error -> error
+    }
+}
+
 /**
  * - Elm: [Result.extract](http://package.elm-lang.org/packages/circuithub/elm-result-extra/1.4.0/Result-Extra#extract)
  * - Rust: [Result.unwrap_or_else](https://doc.rust-lang.org/src/core/result.rs.html#735-740)

src/test/kotlin/com/mikebull94/result/GetTest.kt

@@ -43,6 +43,18 @@ internal class GetTest {
         assertThat(value, equalTo("default"))
     }
 
+    @Test
+    internal fun `getErrorOr should return the default value if ok`() {
+        val error = ok("hello").getErrorOr("world")
+        assertThat(error, equalTo("world"))
+    }
+
+    @Test
+    internal fun `getErrorOr should return the result error if not ok`() {
+        val error = err("hello").getErrorOr("world")
+        assertThat(error, equalTo("hello"))
+    }
+
     @Test
     internal fun `getOrElse should return the result value if ok`() {
         val value = ok("hello").getOrElse { "world" }

src/test/kotlin/com/mikebull94/result/ResultIteratorTest.kt

@@ -2,7 +2,7 @@ package com.mikebull94.result
 
 import com.natpryce.hamkrest.assertion.assertThat
 import com.natpryce.hamkrest.equalTo
-import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Assertions.assertThrows
 import org.junit.jupiter.api.Test
 
 internal class ResultIteratorTest {