C + + setprecision fixed Showpoint

First #include <iomanip>

One: setprecision

Function: Control output stream shows the number of floating-point numbers, Setprecision (n) is the output n number, there will be rounded

Double s=20.7843000;

Cout<<setprecision (1) <<s<<endl; will output 2e+001, because to output a number, so only 2

Cout<<setprecision (2) <<s<<endl; will output 21.

Cout<<setprecision (3) <<s<<endl; output 20.8

Cout<<setprecision (6) <<s<<endl; output 20.7843

Cout<<setprecision (7) <<s<<endl; output 20.7843

Cout<<setprecision (8) <<s<<endl; output 20.7843

Visible, the fractional part at the end of the 0 o'clock, is not output

If you want to output, you have to use Showpoint.

If you add a two statement to the following statements:

cout<<1<<endl;

cout<<1.00800<<endl;

First output: 1. Not a floating-point type

The second article is: 1.008. To undertake the setprecision (8) of this rule statement

If there is a statement directly

int main ()

{

cout<<1<<endl;

cout<<1.00<<endl;

}

First output: 1

The second article is also: 1

II: Setprecision and Showpoint

Declare before output statement: COUT.SETF (ios::showpoint); it's all right.

Double s=20.7843000,

COUT.SETF (Ios::showpoint);

Cout<<setprecision (1) <<s<<endl; will output 2.e+001, notice that there is a "." Between 2 and E.

Cout<<setprecision (2) <<s<<endl; will output 21. Multiple points

Cout<<setprecision (3) <<s<<endl; output 20.8

Cout<<setprecision (6) <<s<<endl; output 20.7843

Cout<<setprecision (7) <<s<<endl; output 20.78430

Cout<<setprecision (8) <<s<<endl; output 20.784300

Visible, the desired number of data will be output

If you add a two statement to the following statements:

cout<<1<<endl;

cout<<1.0080<<endl;

First output: 1 is not a floating-point type.

The second article is also: 1.0080000 to undertake the setprecision (8) of this rule statement.

Three: Setprecision and fixed

If you want to keep a few decimals, the setprecision has to be used with the fixed

Declare before output statement: COUT.SETF (ios::fixed);

Double s=20.7843909

COUT.SETF (ios::fixed);

Cout<<setprecision (1) <<s<<endl; will output 2.8

Cout<<setprecision (2) <<s<<endl; will output 21.78. Multiple points

Cout<<setprecision (3) <<s<<endl; output 20.784

Cout<<setprecision (6) <<s<<endl; output 20.784391

Cout<<setprecision (7) <<s<<endl; output 20.7843909

Cout<<setprecision (8) <<s<<endl; output 20.78439090

If you also add a two statement after these statements:

cout<<1<<endl;

cout<<1.008<<endl;

First output: 1

The second article is: 1.00800000

is to undertake the setprecision (8) of this rule statement, is floating-point type will retain 8 decimal places. Is it an integral type or an integral type?

Statements can also be written as: Cout<<fixed<<setprecision (2) <<s<<endl;

Even if the following statement does not write <<fixed, the same will be treated as <<fixed

Cout<<fixed<<setprecision (2) <<s<<endl;

A:cout<<setprecision (7) <<s<<endl;

B:cout<<setprecision (8) <<s<<endl;

The AB statements are processed in 7 and 8 decimal places, and no more than 7 or 8 floating point numbers are processed.

If you continue to add statement C below:

Cout<<1.008<<endl; will also retain 8 decimal places

Double s=20.7843909

Cout<<setprecision (2) <<s<<endl;//output 21

cout<<fixed<<s<<endl;//Output 20.78

Cout<<setprecision (2) <<s<<endl;//output 21

cout<<showpoint<<s<<endl;//output 21. (There is a point)

cout<<fixed<<s<<endl;//Output 20.78391
cout<<showpoint<<s<<endl;//Output 20.78391

Cout<<setprecision (2) <<s<<endl;//output 21
cout<<fixed<<s<<endl;//Output 20.78
cout<<showpoint<<s<<endl;//Output 20.78

Cout<<setprecision (2) <<s<<endl;//output 21
Cout<<showpoint<<s<<endl;//21. (There is a point)
cout<<fixed<<s<<endl;//20.78

C + + setprecision fixed Showpoint