tree 1e2e897e7e5b51afe6454ee10ec837eb1806a027
parent cfaa1addf4592d44e119604abcec06c73ef113f2
author Junxiao Shi <git@mail1.yoursunny.com> 1472556239 +0000
committer Junxiao Shi <git@mail1.yoursunny.com> 1472556239 +0000

util: backport C++17 optional

This commit also makes code style of parameter packs consistent.

refs #3753

Change-Id: I1e301d25b73501b0b28678e6095bbb5619a0e760