Rather than constraining to floating point, why not just use a 4-bit BCD format with a zeros place symbol and terminator symbol? That way you can express exact

Rather than constraining to floating point, why not just use a 4-bit BCD format with a zeros place symbol and terminator symbol? That way you can express exact values efficiently. Of course it becomes unwieldy when specifying extreme values (such as 10^100), but for most reasonable values (10^20 to 10^-20) it beats both floating point and ASCII for size and speed.