Simple and weird question about accuracy! !! !! Everyone help!

rosbicn

var
  a: double;
  s: string;
begin
  a: = 8.07;
  s: = formatfloat ('#. ######################', a);
  showmessage (s);
end;

Everyone guess what the result is: 8.07000000000000028

why? Why is Delphi so strange?

rosbicn

Why is there another 28 behind it????

It seems that this is the case in any environment, and a relatively fixed number

oldmouse

Because its type is Double

rosbicn

But I assigned it directly. Why does the system force 000000000000028? Is there any good way to solve this problem?

rosbicn

Once I use ADOConnection.Open
a := 8.07000000000000028;

s := formatfloat('#.####################',a);

The s display is still 8.07, why?

面面爱面面

Once I use ADOConnection.Open
a := 8.07000000000000028;
-----------------------------------------------
a := 8.07000000000000028; what is the relationship with using ADOConnection.Open? The landlord did not say.

Assuming that a is extracted from the data table, please ask the landlord to see how accurate the field is.

rosbicn

a := 8.07;
  s := formatfloat('#.#####################',a);
  showmessage(s);//Show 8.00700000000000028
  ADOConnection.Open
  a := 8.07;
  s := formatfloat('#.#####################',a);
  showmessage(s);//Show 8.07

面面爱面面

On 32-bit Windows systems:

Double type: Representation range: ±5.0 * 10^-324 ～ 1.7 * 10^308　　 effective digits: 15~16 digits. So, change your formatFloat like this, try:
var
a: double;
s:string;
begin
  a := 8.07;
  s := formatfloat('#.##############',a);//Note that the decimal point is 15#
  edit1.text := s ;//Display 8.07

  s := format('%1.15f',[a]);
  edit2.text := s; //Display 8.070000000000000　　It is recommended to use format()
end;

Use format() conversion, even if you find the adoconnection problem, it no longer exists.
Your problem, the first is that your precision is beyond the scope of double.

面面爱面面

Oh, about the number of digits, I may be wrong. But using format() is correct.

rosbicn

var
  a:double;
  s:string;
  vADOConnection:Variant;
begin
  a := 8.07;
  s := formatfloat('#.################',a);//s display 8.07000000000000028
  vADOConnection := CreateOleObject('ADODB.Connection');
  vADOConnection.ConnectionString :='Driver={Firebird/InterBase(r) driver};pwd=masterkey;Uid=SYSDBA;database=C:\123.GDB';
  try
    vADOConnection.Open;
  Except
  end;
  a := 8.07;
  s := formatfloat('#.################',a);//s display 8.07
end;


How to achieve the above is 8.07000000000000028? ? ? ? ? ?