feat: iterator.While, slimmed comments in saccharine

pkg/iterator/iterator.go

@@ -81,6 +81,17 @@ func (i Iterator[T]) Done() bool {
 	return i.index == len(i.items)
 }
 
+// While increments the iterator as long as the current item satisfies the
+// predicate. The first item that does not match is left unconsumed.
+func (i *Iterator[T]) While(fn func(T) bool) {
+	for !i.Done() {
+		if !fn(i.MustGet()) {
+			return
+		}
+		i.Forward()
+	}
+}
+
 // Try attempts to perform an operation using the iterator. If the operation
 // succeeds, the iterator is updated. If the operation fails, the iterator is
 // rolled back, and an error is returned.