From be2fa210cc4bcb07ad6f636475d963887e9128d1 Mon Sep 17 00:00:00 2001
From: Michael Bull <mikebull94@gmail.com>
Date: Sat, 21 Oct 2017 18:10:08 +0100
Subject: [PATCH] Add getErrorOr

Matches Haskell's Either.fromRight
---
 src/main/kotlin/com/mikebull94/result/And.kt      |  2 +-
 src/main/kotlin/com/mikebull94/result/Get.kt      | 15 +++++++++++++--
 src/main/kotlin/com/mikebull94/result/Or.kt       |  2 +-
 src/main/kotlin/com/mikebull94/result/Unwrap.kt   |  2 +-
 src/test/kotlin/com/mikebull94/result/GetTest.kt  | 12 ++++++++++++
 .../com/mikebull94/result/ResultIteratorTest.kt   |  2 +-
 6 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/src/main/kotlin/com/mikebull94/result/And.kt b/src/main/kotlin/com/mikebull94/result/And.kt
index c05f7d8..d0f5613 100644
--- a/src/main/kotlin/com/mikebull94/result/And.kt
+++ b/src/main/kotlin/com/mikebull94/result/And.kt
@@ -4,7 +4,7 @@ package com.mikebull94.result
  * Rust: [Result.and](https://doc.rust-lang.org/std/result/enum.Result.html#method.and)
  */
 infix fun <V, E> Result<V, E>.and(result: Result<V, E>): Result<V, E> {
-    return when(this) {
+    return when (this) {
         is Ok -> result
         is Error -> err(error)
     }
diff --git a/src/main/kotlin/com/mikebull94/result/Get.kt b/src/main/kotlin/com/mikebull94/result/Get.kt
index 5387022..8f7146b 100644
--- a/src/main/kotlin/com/mikebull94/result/Get.kt
+++ b/src/main/kotlin/com/mikebull94/result/Get.kt
@@ -15,7 +15,7 @@ fun <V, E> Result<V, E>.get(): V? {
  * - Rust: [Result.err](https://doc.rust-lang.org/std/result/enum.Result.html#method.err)
  */
 fun <V, E> Result<V, E>.getError(): E? {
-    return when(this) {
+    return when (this) {
         is Ok -> null
         is Error -> error
     }
@@ -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 {
@@ -32,11 +33,21 @@ 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)
  */
-infix inline fun <V,E> Result<V,E>.getOrElse(transform: (E) -> V): V {
+infix inline fun <V, E> Result<V, E>.getOrElse(transform: (E) -> V): V {
     return when (this) {
         is Ok -> value
         is Error -> transform(error)
diff --git a/src/main/kotlin/com/mikebull94/result/Or.kt b/src/main/kotlin/com/mikebull94/result/Or.kt
index a5c134c..b929da3 100644
--- a/src/main/kotlin/com/mikebull94/result/Or.kt
+++ b/src/main/kotlin/com/mikebull94/result/Or.kt
@@ -4,7 +4,7 @@ package com.mikebull94.result
  * - Rust: [Result.or](https://doc.rust-lang.org/std/result/enum.Result.html#method.or)
  */
 infix fun <V, E> Result<V, E>.or(result: Result<V, E>): Result<V, E> {
-    return when(this) {
+    return when (this) {
         is Ok -> ok(value)
         is Error -> result
     }
diff --git a/src/main/kotlin/com/mikebull94/result/Unwrap.kt b/src/main/kotlin/com/mikebull94/result/Unwrap.kt
index 16333d0..e5b9cb8 100644
--- a/src/main/kotlin/com/mikebull94/result/Unwrap.kt
+++ b/src/main/kotlin/com/mikebull94/result/Unwrap.kt
@@ -1,6 +1,6 @@
 package com.mikebull94.result
 
-class UnwrapException(message: String): Exception(message)
+class UnwrapException(message: String) : Exception(message)
 
 /**
  * - Rust: [Result.unwrap](https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap)
diff --git a/src/test/kotlin/com/mikebull94/result/GetTest.kt b/src/test/kotlin/com/mikebull94/result/GetTest.kt
index 856ba5f..b7bf5a4 100644
--- a/src/test/kotlin/com/mikebull94/result/GetTest.kt
+++ b/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" }
diff --git a/src/test/kotlin/com/mikebull94/result/ResultIteratorTest.kt b/src/test/kotlin/com/mikebull94/result/ResultIteratorTest.kt
index 72763bb..4f789c3 100644
--- a/src/test/kotlin/com/mikebull94/result/ResultIteratorTest.kt
+++ b/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 {