fromInteger package:Cabal-syntax

fromInteger :: Num a => Integer -> a

Cabal-syntax Distribution.Compat.Prelude

Conversion from an Integer. An integer literal represents the application of the function fromInteger to the appropriate value of type Integer, so such literals have type (Num a) => a.

md5FromInteger :: Integer -> MD5

Cabal-syntax Distribution.Utils.MD5

>>> showMD5 $ md5FromInteger 0x37eff01866ba3f538421b30b7cbefcac
"37eff01866ba3f538421b30b7cbefcac"

Note: the input is truncated:

>>> showMD5 $ md5FromInteger 0x1230000037eff01866ba3f538421b30b7cbefcac
"37eff01866ba3f538421b30b7cbefcac"

Yet, negative numbers are not a problem...

>>> showMD5 $ md5FromInteger (-1)
"ffffffffffffffffffffffffffffffff"