add insertion sort (#1225)

lib/std/sort/insertionsort.c3

@@ -0,0 +1,58 @@
+module std::sort;
+import std::sort::is;
+
+/**
+ * Sort list using the quick sort algorithm.
+ * @require @is_sortable(list) "The list must be indexable and support .len or .len()"
+ * @require $or(@typeid(cmp) == void*.typeid, @is_cmp_fn(cmp, list)) "Expected a comparison function which compares values"
+ **/
+macro insertionsort(list, cmp = null) @builtin
+{
+	usz len = sort::@len_from_list(list);
+	is::isort(<$typeof(list), $typeof(cmp)>)(list, 0, (isz)len, cmp);
+}
+
+module std::sort::is(<Type, Comparer>);
+
+def ElementType = $typeof(Type{}[0]);
+
+fn void isort(Type list, usz low, usz high, Comparer comp)
+{
+	var $no_cmp = Comparer.typeid == void*.typeid;
+	var $cmp_by_value = $and(!$no_cmp, Comparer.params[0] == @typeid(list[0]));
+	var $has_get_ref =  $defined(&list[0]);
+	assert(sort::@is_sortable(list));
+	for (usz i = low; i < high; ++i)
+	{
+		usz j = i;
+		for (;j > low;)
+		{
+			$if $has_get_ref:
+				ElementType *rhs = &list[j];
+				ElementType *lhs = &list[--j];
+				$switch
+					$case $cmp_by_value:
+						if (comp(*rhs, *lhs) >= 0) break;
+					$case !$no_cmp:
+						if (comp(rhs, lhs) >= 0) break;
+					$default:
+						if (!less(*rhs, *lhs)) break;
+				$endswitch
+				@swap(*rhs, *lhs);
+			$else
+				usz r = j;
+				--j;
+
+				$switch
+					$case $cmp_by_value:
+						if (comp(list[r], list[j]) >= 0) break;
+					$case !$no_cmp:
+						if (comp(&list[r], &list[j]) >= 0) break;
+					$default:
+						if (!less(list[r], list[j])) break;
+				$endswitch
+				@swap(list[r], list[j]);
+			$endif
+		}
+	}
+}