Why does bfloat behave this way?

Dear all,

I have just joined this mailing list, so I would like to say first that I have enjoyed using Maxima for quite a while already, since I switched to free software a few years ago. Maxima is great, and my thanks to its creators and maintainers (I also often acknowledge this explicitly in my mathematical papers).

Now the question: why does bfloat behave exactly this way? And not some other way?

(%i1) float2bf: false;
(%o1) false

(%i2) fpprec: 300;
(%o2) 300

(%i3) x: bfloat( 3.4567890123 );
bfloat: converting float 3.4567890123 to bigfloat.
(%o3) 3.45678901229999979705098667182028293609619140625b0

Best wishes,

Igor