Added Sequence.take and Sequence.skip

These lazy iterator producing methods are useful when working with
arbitrary sequences and you need to skip or take some number of elements
at the start.

src/vm/wren_core.wren

@@ -56,6 +56,10 @@ class Sequence {
 
   map(transformation) { MapSequence.new(this, transformation) }
 
+  skip(count) { SkipSequence.new(this, count) }
+
+  take(count) { TakeSequence.new(this, count) }
+
   where(predicate) { WhereSequence.new(this, predicate) }
 
   reduce(acc, f) {
@@ -112,6 +116,43 @@ class MapSequence is Sequence {
   iteratorValue(iterator) { _fn.call(_sequence.iteratorValue(iterator)) }
 }
 
+class SkipSequence is Sequence {
+  construct new(sequence, count) {
+    _sequence = sequence
+    _count = count
+  }
+
+  iterate(iterator) {
+    if (iterator) {
+      return _sequence.iterate(iterator)
+    } else {
+      iterator = _sequence.iterate(iterator)
+      var count = _count
+      while (count > 0 && iterator) {
+        iterator = _sequence.iterate(iterator)
+        count = count - 1
+      }
+      return iterator
+    }
+  }
+
+  iteratorValue(iterator) { _sequence.iteratorValue(iterator) }
+}
+
+class TakeSequence is Sequence {
+  construct new(sequence, count) {
+    _sequence = sequence
+    _count = count
+  }
+
+  iterate(iterator) {
+    if (!iterator) _taken = 1 else _taken = _taken + 1
+    return _taken > _count ? null : _sequence.iterate(iterator)
+  }
+
+  iteratorValue(iterator) { _sequence.iteratorValue(iterator) }
+}
+
 class WhereSequence is Sequence {
   construct new(sequence, fn) {
     _sequence = sequence

src/vm/wren_core.wren.inc

@@ -58,6 +58,10 @@ static const char* coreModuleSource =
 "\n"
 "  map(transformation) { MapSequence.new(this, transformation) }\n"
 "\n"
+"  skip(count) { SkipSequence.new(this, count) }\n"
+"\n"
+"  take(count) { TakeSequence.new(this, count) }\n"
+"\n"
 "  where(predicate) { WhereSequence.new(this, predicate) }\n"
 "\n"
 "  reduce(acc, f) {\n"
@@ -114,6 +118,43 @@ static const char* coreModuleSource =
 "  iteratorValue(iterator) { _fn.call(_sequence.iteratorValue(iterator)) }\n"
 "}\n"
 "\n"
+"class SkipSequence is Sequence {\n"
+"  construct new(sequence, count) {\n"
+"    _sequence = sequence\n"
+"    _count = count\n"
+"  }\n"
+"\n"
+"  iterate(iterator) {\n"
+"    if (iterator) {\n"
+"      return _sequence.iterate(iterator)\n"
+"    } else {\n"
+"      iterator = _sequence.iterate(iterator)\n"
+"      var count = _count\n"
+"      while (count > 0 && iterator) {\n"
+"        iterator = _sequence.iterate(iterator)\n"
+"        count = count - 1\n"
+"      }\n"
+"      return iterator\n"
+"    }\n"
+"  }\n"
+"\n"
+"  iteratorValue(iterator) { _sequence.iteratorValue(iterator) }\n"
+"}\n"
+"\n"
+"class TakeSequence is Sequence {\n"
+"  construct new(sequence, count) {\n"
+"    _sequence = sequence\n"
+"    _count = count\n"
+"  }\n"
+"\n"
+"  iterate(iterator) {\n"
+"    if (!iterator) _taken = 1 else _taken = _taken + 1\n"
+"    return _taken > _count ? null : _sequence.iterate(iterator)\n"
+"  }\n"
+"\n"
+"  iteratorValue(iterator) { _sequence.iteratorValue(iterator) }\n"
+"}\n"
+"\n"
 "class WhereSequence is Sequence {\n"
 "  construct new(sequence, fn) {\n"
 "    _sequence = sequence\n"