Inconsistent behavior with NaN

[gahag]

Describe the bug
Jq does not accept nan, but accepts -nan.

To Reproduce

echo nan | jq .
parse error: Invalid literal at line 2, column 0

echo -nan | jq .
null

echo NaN | jq .
null

echo -NaN | jq .
null

Expected behavior
Not sure if jq should accept nan, or reject -nan. I would vote for rejecting -nan, as some popular applications like MongoDB do.

Environment (please complete the following information):

• OS: Kubuntu 19.04
• jq version: jq-1.5-1-a5b5cbe