id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5525	Mismatch between documentation and behaviour of encodeFloat	daniel.is.fischer		"In the process of elaborating the docs to treat #3898, I wrote
{{{
    -- | 'encodeFloat' performs the inverse of 'decodeFloat' in the
    -- sense that for finite @x@ with the exception of @-0.0@,
    -- @'uncurry' 'encodeFloat' ('decodeFloat' x) = x@.
    -- @'encodeFloat' m n@ is the closest representable floating-point
    -- number to @m*b^^n@ (or @±Infinity@ if overflow occurs).
}}}
Unfortunately, the last sentence is not quite true. If the end result is a subnormal number, `encodeFloat` performs two roundings, which may lead to a wrong result (can be 1 ulp off). Changing `encodeFloat` so that it always finds the closest representable number would cost a lot in performance, it would bring it close to `fromRational`. So the thing to do is change the docs, I just don't know how yet."	bug	closed	normal		libraries/base	7.3	fixed			Unknown/Multiple	Unknown/Multiple	Documentation bug