Fix typo in Singleton
Fix typo in Singleton

Summary: The "l" in "Haskell" is not a singleton. Also, friends don't let friends rely on operator precedence.

Reviewed By: yfeldblum

Differential Revision: D4756653

fbshipit-source-id: 7b5360bfc1b26fac06062e4adbfae3a1e477c2dc

rklabs/folly,facebook/folly,Orvid/folly,rklabs/folly,facebook/folly,Orvid/folly,facebook/folly,rklabs/folly,rklabs/folly,rklabs/folly,Orvid/folly,Orvid/folly,facebook/folly,Orvid/folly,facebook/folly