Add refined floating-point types

[rider-yi]

I added some floating-point types for convenience.

[codecov]

Codecov Report

Merging #414 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #414   +/-   ##
=======================================
  Coverage   95.54%   95.54%           
=======================================
  Files          46       46           
  Lines         561      561           
  Branches       12       12           
=======================================
  Hits          536      536           
  Misses         25       25

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[fthomas]

LGTM, thanks @rider-yi!