BUG #1888: bug in cast from float4 to float8

The following bug has been logged online:

Bug reference:      1888
Logged by:          Pablo Oses
Email address:      opablo@gmail.com
PostgreSQL version: 8.0.x and 7.2.x
Operating system:   redhat, slackware and win32
Description:        bug in cast from float4 to float8
Details:

this is *really* simple

execute something like this:
select cast(123.456::float4 as float8)

what do you think its the answer ? 123.456 ?

well pgsql 7.2.2, 8.0.0, 8.0.1 and 8.0.3 (all i have used) answers this:
123.456001281738 which is WRONG

bye and thanks for a wonderfull contribution for the free software comunity