Additional pipe methods (#71)

src/box.ghul

@@ -0,0 +1,14 @@
+namespace Ghul is
+    class BOX[T] is 
+        value: T public;
+
+        init() is
+        si
+
+        init(value: T) is
+            self.value = value;
+        si
+
+        to_string() -> string => "{value}";
+    si
+si

src/flat-map-pipe.ghul

@@ -0,0 +1,42 @@
+namespace Ghul.Pipes is
+    use Collections;
+
+    class FLAT_MAP_PIPE[TFrom,TTo]: Pipe[TTo] is
+        current: TTo;
+
+        _iterator: Iterator[TFrom];
+        _flat_iterator: Iterator[TTo];
+
+        _mapper: (TFrom) -> Iterable[TTo];
+
+        init(iterator: Iterator[TFrom], mapper: (TFrom) -> Iterable[TTo]) is
+            _iterator = iterator;
+            _mapper = mapper;
+        si
+
+        move_next() -> bool is
+            do
+                if _flat_iterator? /\ _flat_iterator.move_next() then
+                    current = _flat_iterator.current;
+
+                    return true;
+                fi
+
+                if !_iterator.move_next() then
+                    reset();
+
+                    return false;
+                fi
+
+                let flat_iterable = _mapper(_iterator.current);
+
+                _flat_iterator = flat_iterable.iterator;
+            od
+        si
+
+        reset() is
+            _iterator.reset();
+            _flat_iterator = null;
+        si
+    si
+si

src/list-reverse-pipe.ghul

@@ -0,0 +1,34 @@
+namespace Ghul.Pipes is
+    use Collections;
+
+    class LIST_REVERSE_PIPE[T]: Pipe[T] is
+        _list: List[T];
+        _index: int;
+
+        current: T => _list[_index];
+
+        init(list: List[T]) is
+            super.init(list);
+
+            _list = list;
+            reset();
+        si
+
+        move_next() -> bool is
+            let result = _index > 0;
+
+            if result then
+                _index = _index - 1;
+            fi
+
+            return result;
+        si
+
+        reset() is
+            _index = _list.count;
+        si
+
+        dispose() is
+        si
+    si
+si

src/pipe.ghul

@@ -58,6 +58,9 @@ namespace Ghul.Pipes is
         map[U](mapper: (T) -> U) -> Pipe[U] =>
             MAP_PIPE[T,U](iterator, mapper);
 
+        flat_map[U](mapper: (T) -> Iterable[U]) -> Pipe[U] =>
+            FLAT_MAP_PIPE[T,U](iterator, mapper);
+
         skip(count: int) -> Pipe[T] =>
             SKIP_PIPE[T](iterator, count);
 
@@ -167,6 +170,19 @@ namespace Ghul.Pipes is
 
             throw InvalidOperationException("no matching element found");
         si
+
+        find_map_or_throw[U](mapper: (T) -> MAYBE[U]) -> U is
+            while move_next() do
+                let element = current;
+                let maybe_result = mapper(element);
+
+                if maybe_result? then
+                    return maybe_result!;
+                fi
+            od
+
+            throw InvalidOperationException("no matching element found");
+        si        
 
         first() -> MAYBE[T] =>
             if move_next() then
@@ -185,7 +201,7 @@ namespace Ghul.Pipes is
                 fi
             fi
 
-            MAYBE[U]();
+            return MAYBE[U]();
         si
 
         first_or_throw() -> T =>
@@ -194,7 +210,20 @@ namespace Ghul.Pipes is
             else
                 throw InvalidOperationException("no element found")
             fi;
+
+        first_map_or_throw[U](mapper: (T) -> MAYBE[U]) -> U is
+            if move_next() then
+                let element = current;
+                let maybe_result = mapper(element);
 
+                if maybe_result? then
+                    return maybe_result!
+                fi
+            fi
+
+            throw InvalidOperationException("no matching element found");
+        si
+
         only() -> T is
             if move_next() then
                 let result = current;
@@ -250,6 +279,16 @@ namespace Ghul.Pipes is
             return true;
         si
 
+        for_each(action: T -> void) is
+            while move_next() do
+                action(current);
+            od
+        si
+
+        reverse() -> Pipe[T] =>
+            let list = collect_list() in
+            LIST_REVERSE_PIPE(list);
+
         sort() -> Pipe[T] is
             let list = collect_list();
 

tests/flat-map-pipe-tests.ghul

@@ -0,0 +1,136 @@
+namespace Tests is
+
+    use Collections;
+    use NSubstitute;
+
+    use NSubstitute.SubstituteExtensions.returns;
+    use NSubstitute.SubstituteExtensions.received;
+
+    use Microsoft.VisualStudio.TestTools.UnitTesting;
+
+    use Ghul.Pipes;
+
+    class FlatMapPipeShould is
+        @test()
+
+        init() is
+        si
+
+        FlatMap_EmptyArray_ReturnsEmptySequence() is
+            @test()
+
+            let pipe = 
+                Ghul.Pipes.Pipe`[int]
+                    .from(empty`[int]());
+
+            let result = 
+                pipe
+                    .flat_map(i => i.to_string());
+
+            assert_are_equal(empty`[char](), result);
+        si
+
+        FlatMap_IntsToStrings_ReturnsExpectedSequence() is
+            @test()
+
+            let pipe = 
+                Ghul.Pipes.Pipe`[int]
+                    .from([3, 4, 1, 5, 2, 3, 1, 4, 5]);
+
+            let result = 
+                pipe
+                    .flat_map(i => i.to_string());
+
+            assert_are_equal(['3', '4', '1', '5', '2', '3', '1', '4', '5'], result);
+        si
+
+        FlatMap_ArraysIdentity_ReturnsConcatArrays() is
+            @test()
+
+            let pipe = 
+                Ghul.Pipes.Pipe[int[]]
+                    .from([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);
+
+            let result =
+                pipe
+                    .flat_map(a => a);
+
+            assert_are_equal([1, 2, 3, 4, 5, 6, 7, 8, 9], result);
+        si
+
+        FlatMap_ResetBeforeIteration_HasNoEffect() is
+            @test()
+
+            let pipe = 
+                Ghul.Pipes.Pipe[int[]]
+                    .from([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);
+
+            let result =
+                pipe
+                    .flat_map(a => a);
+
+            result.reset();
+
+            assert_are_equal([1, 2, 3, 4, 5, 6, 7, 8, 9], result);
+        si
+
+        FlatMap_ResetAfterIncompleteIteration_StartsAgainFromBeginning() is
+            @test()
+
+            let pipe = 
+                Ghul.Pipes.Pipe[int[]]
+                    .from([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);
+
+            let result =
+                pipe
+                    .flat_map(a => a);
+
+            result.move_next();
+            result.move_next();
+            result.move_next();
+            result.move_next();
+
+            result.reset();
+
+            assert_are_equal([1, 2, 3, 4, 5, 6, 7, 8, 9], result);
+        si
+
+        FlatMap_CompleteIteration_ResetsPipe() is
+            @test()
+
+            let pipe = 
+                Ghul.Pipes.Pipe[int[]]
+                    .from([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);
+
+            let result =
+                pipe
+                    .flat_map(a => a);
+
+            // count consumes the whole pipe and then resets it:
+            let count = result.count();
+
+            assert_are_equal([1, 2, 3, 4, 5, 6, 7, 8, 9], result);
+        si
+
+
+        FlatMap_ResetAfterIteration_HasNoEffect() is
+            @test()
+
+            let pipe = 
+                Ghul.Pipes.Pipe[int[]]
+                    .from([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);
+
+            let result =
+                pipe
+                    .flat_map(a => a);
+
+            // count consumes the whole pipe and then resets it:
+            let count = result.count();
+
+            // this reset is a no-op:
+            result.reset();
+
+            assert_are_equal([1, 2, 3, 4, 5, 6, 7, 8, 9], result);
+        si
+    si
+si

tests/pipe-tests.ghul

@@ -503,6 +503,54 @@ namespace Tests is
             Assert.are_equal("total: " + (1 + 2 + 3 + 4 + 5 + 6), result);
         si
 
+        Reverse_EmptySequence_GivesEmptyResult() is
+            @test()
+
+            let pipe = Pipe.from(empty[int]());
+
+            let result = pipe.reverse();
+
+            assert_are_equal(empty[int](), result);
+        si
+
+        Reverse_NonEmptySequence_GivesExpectedResult() is
+            @test()
+
+            let pipe = Pipe.from([1, 2, 3, 4, 5, 6]);
+
+            let result = pipe.reverse();
+
+            assert_are_equal([6, 5, 4, 3, 2, 1], result);
+        si
+
+        ForEach_EmptySequence_DoesNotCallAction() is
+            @test()
+
+            let pipe = Pipe.from(empty[int]());
+
+            let action_was_called = BOX(false);
+
+            pipe.for_each(element is
+                action_was_called.value = true;
+            si);
+
+            Assert.is_false(action_was_called.value);
+        si
+
+        ForEach_NonEmptySequence_CallsActionOnceInOrderForEveryElement() is
+            @test()
+
+            let pipe = Pipe.from([1, 2, 3, 4, 5, 6]);
+
+            let result = LIST[int]();
+
+            pipe.for_each(element is
+                result.add(element)
+            si);
+
+            assert_are_equal([1, 2, 3, 4, 5, 6], Pipe.from(result));
+        si
+
         Sort_NoComparer_SortsInDefaultOrder() is
             @test()