negative value, divide, etc

terefere

453 // 10 give 45. here is ok
-453 // 10 give -46. Why not -45?!

Generally, how to keep negative value in lua. If I give -12 in set_value function, then screen show it also as -12. But if get from modbus value 0xFFFF, then screen show it as 65535 instead -1. If I see good then Dacai use external function who translate it to negative before display. If yes, then I see here many else problem, like "if" statment who will see 0xFFFF as higher than 0x0

If后要接end

"//" in lua means to fetch remainder downward, which is consistent with the usage of math. floor ()

If后要接end

In addition, if your register data is a signed integer, you need to judge whether the highest bit of the register data is 1 in the script to distinguish whether the data is an integer or a negative number

terefere

If后要接end 发表于 2022-10-8 08:58
"//" in lua means to fetch remainder downward, which is consistent with the usage of math. floor ()

Yes, but with negative value made "upward".  I use math.modf

1.         a= 0xFF16        -- -234
   
2.         
   
3.         --16bit register is negative?
   
4.         if (a & 0x8000 ~=0) then
   
5.                 a=  (~a +1) & 0xFFFF
   
6.                 a = -a
   
7.         end
   
8. 
   
9.         string_buf = string.format ( "%1d,%d" ,math.modf(a/10), math.abs(a)%10)
   
10.         set_text(Screen,27,string_buf)

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After conversion, Instead magic with string buf, to see variable wit the same result I can simple write

1. set_text(Screen,27,a/10)

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but I need this magic to add some char to variable text.

If后要接end

terefere 发表于 2022-10-8 23:22
Yes, but with negative value made "upward".  I use math.modf

math.modfis to split the data into integer parts and decimal parts. For example, a, b=math. modf (20.34) yields a=20 and b=0.34, respectively

If后要接end

terefere 发表于 2022-10-8 23:22
Yes, but with negative value made "upward".  I use math.modf

If you want to determine whether a number is negative, you can determine whether the highest bit is 1, and then subtract 65536 from this data to get the negative number.