stan-dev/stan — pull request #876 by PeterLi2016 (2014-08-14 19:00:01+00:00)
Title: Feature/issue 861 erfc nan

#### Summary:
Fixes issue #861 .

#### Intended Effect:
agrad/rev/erfc should now return NaN for gradients and value when passed in NaN.

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

#### Side Effects:
None.

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

#### Reviewer Suggestions:
Anyone