What purpose does に serve in set phrases that go after verbs?


> ～するに決まっている
>
> ～するに留まった
>
> ～するにして・にしろ・にしては,etc

[other than this
usage](https://japanese.stackexchange.com/questions/29418/what-does-
the-%e3%81%ab-do-
in-%e8%a1%a8%e6%83%85%e3%81%8b%e3%82%89%e5%af%9f%e3%81%99%e3%82%8b%e3%81%ab)
you don't see に after verbs. The entire に＿＿＿ is explained as grammar point as
a whole.

