Fix stream iterate factory (#91)

Author: akondas

src/Collection/Stream.php

@@ -105,10 +105,8 @@ public static function continually(callable $supplier): self
      */
     public static function iterate($seed, callable $iterator): self
     {
-        $current = $iterator($seed);
-
-        return new Cons($current, function () use ($iterator, $current) {
-            return self::iterate($current, $iterator);
+        return new Cons($seed, function () use ($iterator, $seed) {
+            return self::iterate($iterator($seed), $iterator);
         });
     }
 

tests/Collection/StreamTest.php

@@ -143,8 +143,9 @@ public function testStreamContinually(): void
 
     public function testStreamIterate(): void
     {
-        self::assertTrue(Stream::of(2, 4, 8)->equals(Stream::iterate(1, function (int $i) {return $i * 2; })->take(3)));
-        self::assertTrue(Stream::of(-1, -2, -3)->equals(Stream::iterate(0, function (int $i) {return --$i; })->take(3)));
+        self::assertTrue(Stream::of(1, 2, 4)->equals(Stream::iterate(1, function (int $i) {return $i * 2; })->take(3)));
+        self::assertTrue(Stream::of(0, -1, -2)->equals(Stream::iterate(0, function (int $i) {return --$i; })->take(3)));
+        self::assertTrue(Stream::of('a', 'aa', 'aaaa')->equals(Stream::iterate('a', function (string $t) {return $t.$t; })->take(3)));
     }
 
     public function testStreamCons(): void