一般来说提到半助动词都会说到： be going to，但几乎没有人说 be coming to 也是半助动词。
但下面这句话参考书上说 are coming to recognize 整体做谓语：
What’s more, researchers are coming to recognize that dreaming is an
essential part of understanding, organizing and retaining what we learn—and
that dreams may even hold out the possibility of directing our learning as we
doze.
言下之意肯定是 are coming to recognize 是半助动词，不能单独做谓语。为什么会这样？
be coming to 也是半助动词吗？它可以和 be going to互换吗？
补充说明：所谓属于“半助动词”，即自身一般不能做单独做谓语，必须与其后面的动词原形一起构成复合谓语。
