Add feature parity with Rust's Result type

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

@@ -1,9 +1,20 @@
 package com.mikebull94.result
 
 /**
- * - Elm: [Result.andThen](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#andThen)
+ * Rust: [Result.and](https://doc.rust-lang.org/std/result/enum.Result.html#method.and)
  */
-inline fun <V, E, U> Result<V, E>.andThen(transform: (V) -> Result<U, E>): Result<U, E> {
+infix fun <V, E> Result<V, E>.and(result: Result<V, E>): Result<V, E> {
+    return when(this) {
+        is Ok -> result
+        is Error -> err(error)
+    }
+}
+
+/**
+ * - Elm: [Result.andThen](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#andThen)
+ * - Rust: [Result.and_then](https://doc.rust-lang.org/std/result/enum.Result.html#method.and_then)
+ */
+infix inline fun <V, E, U> Result<V, E>.andThen(transform: (V) -> Result<U, E>): Result<U, E> {
     return when (this) {
         is Ok -> transform(value)
         is Error -> err(error)

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

@@ -2,6 +2,7 @@ package com.mikebull94.result
 
 /**
  * - Elm: [Result.toMaybe](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#toMaybe)
+ * - Rust: [Result.ok](https://doc.rust-lang.org/std/result/enum.Result.html#method.ok)
  */
 fun <V, E> Result<V, E>.get(): V? {
     return when (this) {
@@ -11,11 +12,33 @@ fun <V, E> Result<V, E>.get(): V? {
 }
 
 /**
- * - Elm: [Result.withDefault](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#withDefault)
+ * - Rust: [Result.err](https://doc.rust-lang.org/std/result/enum.Result.html#method.err)
  */
-infix fun <V, E> Result<V, E>.getOrElse(default: V): V {
+fun <V, E> Result<V, E>.getError(): E? {
+    return when(this) {
+        is Ok -> null
+        is Error -> error
+    }
+}
+
+/**
+ * - Elm: [Result.withDefault](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#withDefault)
+ * - 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 {
     return when (this) {
         is Ok -> value
         is Error -> default
     }
 }
+
+/**
+ * - 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 {
+    return when (this) {
+        is Ok -> value
+        is Error -> transform(error)
+    }
+}

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

@@ -3,8 +3,9 @@ package com.mikebull94.result
 /**
  * - Elm: [Result.map](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#map)
  * - Haskell: [Data.Bifunctor.first](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Bifunctor.html#v:first)
+ * - Rust: [Result.map](https://doc.rust-lang.org/std/result/enum.Result.html#method.map)
  */
-inline fun <V, E, U> Result<V, E>.map(transform: (V) -> U): Result<U, E> {
+infix inline fun <V, E, U> Result<V, E>.map(transform: (V) -> U): Result<U, E> {
     return when (this) {
         is Ok -> ok(transform(value))
         is Error -> err(error)
@@ -14,8 +15,9 @@ inline fun <V, E, U> Result<V, E>.map(transform: (V) -> U): Result<U, E> {
 /**
  * - Elm: [Result.mapError](http://package.elm-lang.org/packages/elm-lang/core/latest/Result#mapError)
  * - Haskell: [Data.Bifunctor.right](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Bifunctor.html#v:second)
+ * - Rust: [Result.map_err](https://doc.rust-lang.org/std/result/enum.Result.html#method.map_err)
  */
-inline fun <V, E, U> Result<V, E>.mapError(transform: (E) -> U): Result<V, U> {
+infix inline fun <V, E, U> Result<V, E>.mapError(transform: (E) -> U): Result<V, U> {
     return when (this) {
         is Ok -> ok(value)
         is Error -> err(transform(error))

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

@@ -1,18 +1,21 @@
 package com.mikebull94.result
 
-infix fun <V, E> Result<V, E>.or(default: V): Result<V, E> {
-    return when (this) {
-        is Ok -> this
-        is Error -> ok(default)
+/**
+ * - 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) {
+        is Ok -> ok(value)
+        is Error -> result
     }
 }
 
 /**
- * - Elm: [Result.extract](http://package.elm-lang.org/packages/circuithub/elm-result-extra/1.4.0/Result-Extra#extract)
+ * - Rust: [Result.or_else](https://doc.rust-lang.org/std/result/enum.Result.html#method.or_else)
  */
-inline fun <V, E> Result<V, E>.extract(transform: (E) -> V): V {
+infix inline fun <V, E> Result<V, E>.orElse(transform: (E) -> Result<V, E>): Result<V, E> {
     return when (this) {
-        is Ok -> value
+        is Ok -> ok(this.value)
         is Error -> transform(error)
     }
 }

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

@@ -3,6 +3,7 @@ package com.mikebull94.result
 /**
  * - Elm: [Result](http://package.elm-lang.org/packages/elm-lang/core/5.1.1/Result)
  * - Haskell: [Data.Either](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Either.html)
+ * - Rust: [Result](https://doc.rust-lang.org/std/result/enum.Result.html)
  */
 sealed class Result<out V, out E>
 

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

@@ -0,0 +1,43 @@
+package com.mikebull94.result
+
+/**
+ * - Rust: [Result.iter](https://doc.rust-lang.org/std/result/enum.Result.html#method.iter)
+ */
+fun <V, E> Result<V, E>.iterator(): Iterator<V> {
+    return ResultIterator(this)
+}
+
+/**
+ * Rust: [Result.iter_mut](https://doc.rust-lang.org/std/result/enum.Result.html#method.iter_mut)
+ */
+fun <V, E> Result<V, E>.mutableIterator(): MutableIterator<V> {
+    return ResultIterator(this)
+}
+
+private class ResultIterator<out V, out E>(private val result: Result<V, E>) : MutableIterator<V> {
+    private var yielded = false
+
+    override fun hasNext(): Boolean {
+        if (yielded) {
+            return false
+        }
+
+        return when (result) {
+            is Ok -> true
+            is Error -> false
+        }
+    }
+
+    override fun next(): V {
+        if (!yielded && result is Ok) {
+            yielded = true
+            return result.value
+        } else {
+            throw NoSuchElementException()
+        }
+    }
+
+    override fun remove() {
+        yielded = true
+    }
+}

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

@@ -0,0 +1,43 @@
+package com.mikebull94.result
+
+class UnwrapException(message: String): Exception(message)
+
+/**
+ * - Rust: [Result.unwrap](https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap)
+ */
+fun <V, E> Result<V, E>.unwrap(): V {
+    return when (this) {
+        is Ok -> value
+        is Error -> throw UnwrapException("called Result.wrap on an Error value $error")
+    }
+}
+
+/**
+ * - Rust: [Result.expect](https://doc.rust-lang.org/std/result/enum.Result.html#method.expect)
+ */
+infix fun <V, E> Result<V, E>.expect(message: String): V {
+    return when (this) {
+        is Ok -> value
+        is Error -> throw UnwrapException(message)
+    }
+}
+
+/**
+ * - Rust: [Result.unwrap_err](https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap_err)
+ */
+fun <V, E> Result<V, E>.unwrapError(): E {
+    return when (this) {
+        is Ok -> throw UnwrapException("called Result.unwrapError on an Ok value $value")
+        is Error -> error
+    }
+}
+
+/**
+ * - Rust: [Reseult.expect_err](https://doc.rust-lang.org/std/result/enum.Result.html#method.expect_err)
+ */
+infix fun <V, E> Result<V, E>.expectError(message: String): E {
+    return when (this) {
+        is Ok -> throw UnwrapException(message)
+        is Error -> error
+    }
+}

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

@@ -8,6 +8,18 @@ import org.junit.jupiter.api.Test
 internal class AndTest {
     private object AndError
 
+    @Test
+    internal fun `and should return the result value if ok`() {
+        val value = ok(230).and(ok(500)).get()
+        assertThat(value, equalTo(500))
+    }
+
+    @Test
+    internal fun `and should return the result value if not ok`() {
+        val error = ok(300).and(err("hello world")).getError()
+        assertThat(error, equalTo("hello world"))
+    }
+
     @Test
     internal fun `andThen should return the transformed result value if ok`() {
         val value = ok(5).andThen { ok(it + 7) }.get()
@@ -16,10 +28,7 @@ internal class AndTest {
 
     @Test
     internal fun `andThen should return the result error if not ok`() {
-        val result = ok(20).andThen { ok(it + 43) }.andThen { err(AndError) }
-
-        result as Error
-
-        assertThat(result.error, sameInstance(AndError))
+        val error = ok(20).andThen { ok(it + 43) }.andThen { err(AndError) }.getError()!!
+        assertThat(error, sameInstance(AndError))
     }
 }

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

@@ -20,14 +20,38 @@ internal class GetTest {
     }
 
     @Test
-    internal fun `getOrElse should return the result value if ok`() {
-        val value = ok("hello").getOrElse("world")
+    internal fun `getError should return null if ok`() {
+        val error = ok("example").getError()
+        assertThat(error, equalTo(null))
+    }
+
+    @Test
+    internal fun `getError should return the result error if not ok`() {
+        val error = err("example").getError()
+        assertThat(error, equalTo("example"))
+    }
+
+    @Test
+    internal fun `getOr should return the result value if ok`() {
+        val value = ok("hello").getOr("world")
         assertThat(value, equalTo("hello"))
     }
 
     @Test
-    internal fun `getOrElse should return default value if not ok`() {
-        val value = err(GetError).getOrElse("default")
+    internal fun `getOr should return default value if not ok`() {
+        val value = err(GetError).getOr("default")
         assertThat(value, equalTo("default"))
     }
+
+    @Test
+    internal fun `getOrElse should return the result value if ok`() {
+        val value = ok("hello").getOrElse { "world" }
+        assertThat(value, equalTo("hello"))
+    }
+
+    @Test
+    internal fun `getOrElse should return the transformed result error if ok`() {
+        val value = err("hello").getOrElse { "world" }
+        assertThat(value, equalTo("world"))
+    }
 }

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

@@ -9,25 +9,25 @@ internal class OrTest {
 
     @Test
     internal fun `or should return the result value if ok`() {
-        val value = ok(500).or(1000).get()
+        val value = ok(500).or(ok(1000)).get()
         assertThat(value, equalTo(500))
     }
 
     @Test
     internal fun `or should return the default value if not ok`() {
-        val error = err(OrError).or(5000).get()
+        val error = err(OrError).or(ok(5000)).get()
         assertThat(error, equalTo(5000))
     }
 
     @Test
-    internal fun `extract should return the result value if ok`() {
-        val value = ok("hello").extract { OrError } as String
-        assertThat(value, equalTo("hello"))
+    internal fun `orElse should return the result value if ok`() {
+        val value = ok(3000).orElse { ok(4000) }.get()
+        assertThat(value, equalTo(3000))
     }
 
     @Test
-    internal fun `extract should return the transformed result error if not ok`() {
-        val error = err("hello").extract { "$it darkness" }
-        assertThat(error, equalTo("hello darkness"))
+    internal fun `orElse should return the transformed value if not ok`() {
+        val error = err(4000).orElse { ok(2000) }.get()
+        assertThat(error, equalTo(2000))
     }
 }

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

@@ -0,0 +1,69 @@
+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.Test
+
+internal class ResultIteratorTest {
+    @Test
+    internal fun `hasNext should return true if unyielded and result is ok`() {
+        val iterator = ok("hello").iterator()
+        assertThat(iterator.hasNext(), equalTo(true))
+    }
+
+    @Test
+    internal fun `hasNext should return false if result is not ok`() {
+        val iterator = err("hello").iterator()
+        assertThat(iterator.hasNext(), equalTo(false))
+    }
+
+    @Test
+    internal fun `hasNext should return false if yielded`() {
+        val iterator = ok("hello").iterator()
+        iterator.next()
+        assertThat(iterator.hasNext(), equalTo(false))
+    }
+
+    @Test
+    internal fun `next should return the result value if unyielded and result is ok`() {
+        val value = ok("hello").iterator().next()
+        assertThat(value, equalTo("hello"))
+    }
+
+    @Test
+    internal fun `next should throw NoSuchElementException if unyielded and result is not ok`() {
+        val iterator = err("hello").iterator()
+
+        assertThrows(NoSuchElementException::class.java) {
+            iterator.next()
+        }
+    }
+
+    @Test
+    internal fun `next should throw NoSuchElementException if yielded and result is ok`() {
+        val iterator = ok("hello").iterator()
+        iterator.next()
+
+        assertThrows(NoSuchElementException::class.java) {
+            iterator.next()
+        }
+    }
+
+    @Test
+    internal fun `remove should make hasNext return false`() {
+        val iterator = ok("hello").mutableIterator()
+        iterator.remove()
+        assertThat(iterator.hasNext(), equalTo(false))
+    }
+
+    @Test
+    internal fun `remove should make next throw NoSuchElementException`() {
+        val iterator = ok("hello").mutableIterator()
+        iterator.remove()
+
+        assertThrows(NoSuchElementException::class.java) {
+            iterator.next()
+        }
+    }
+}

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

@@ -0,0 +1,60 @@
+package com.mikebull94.result
+
+import com.natpryce.hamkrest.assertion.assertThat
+import com.natpryce.hamkrest.equalTo
+import org.junit.jupiter.api.Assertions.assertThrows
+import org.junit.jupiter.api.Test
+
+internal class UnwrapTest {
+    @Test
+    internal fun `unwrap should return the result value if ok`() {
+        val value = ok(5000).unwrap()
+        assertThat(value, equalTo(5000))
+    }
+
+    @Test
+    internal fun `unwrap should throw an UnwrapException if not ok`() {
+        assertThrows(UnwrapException::class.java, {
+            err(5000).unwrap()
+        }, "called Result.wrap on an Error value 5000")
+    }
+
+    @Test
+    internal fun `expect should return the result value if ok`() {
+        val value = ok(1994).expect("the year should be 1994")
+        assertThat(value, equalTo(1994))
+    }
+
+    @Test
+    internal fun `expect should throw an UnwrapException with a specified message if not ok`() {
+        assertThrows(UnwrapException::class.java, {
+            err(1994).expect("the year should be 1994")
+        }, "the year should be 1994")
+    }
+
+    @Test
+    internal fun `unwrapError should throw an UnwrapException if ok`() {
+        assertThrows(UnwrapException::class.java, {
+            ok("example").unwrapError()
+        }, "called Result.unwrapError on an Ok value example")
+    }
+
+    @Test
+    internal fun `unwrapError should return the result error if not ok`() {
+        val error = err("example").unwrapError()
+        assertThat(error, equalTo("example"))
+    }
+
+    @Test
+    internal fun `expectError should throw an UnwrapException with a specified message if ok`() {
+        assertThrows(UnwrapException::class.java, {
+            ok(2010).expectError("the year should be 2010")
+        }, "the year should be 2010")
+    }
+
+    @Test
+    internal fun `expectError should return the result error if not ok`() {
+        val error = err(2010).expectError("the year should be 2010")
+        assertThat(error, equalTo(2010))
+    }
+}