stan-dev/stan — pull request #888 by PeterLi2016 (2014-08-18 19:33:02+00:00)
Title: Bugfix/issue 887 fdim rev nan

#### Summary:
Fixes issue #887 .

#### Intended Effect:
agrad/rev/fdim should now return NaN when either argument is NaN.

#### How to Verify:
Run test/unit-agrad-rev/functions/fdim.

#### Side Effects:
None.

#### Documentation:
None. Should document behavior of function when given NaN together with other functions.

#### Reviewer Suggestions:
Anyone