LUA, divide negative value

Question

For example, I have vaule "a" = -23 who I want to print as -2.3

I write this code who work good when a > 0, also work in other language string_buf = string.format ( "%1d,%d",a //10, math.abs(a) %10) but when I use only use "//" then I have one more and instead -2.3 see to -3.3

Where is problem?.

Answer 1

Ok, I try modf. Works.

    a= 0xFF16   -- -234

--16bit register is negative?
if (a & 0x8000 ~=0) then 
    a=  (~a +1) & 0xFFFF
    a = -a 
end

string_buf = string.format ( "%1d,%d" ,math.modf(a/10), math.abs(a)%10)