Setprecision, fixed, and showpoint usage summary, setprecisionfixed

Setprecision, fixed, and showpoint usage summary, setprecisionfixed

First, add the header file: iomanip

I. setprecision

Purpose: control the number of floating-point numbers displayed in the output stream. setprecision (n) is the number of n output values, which are rounded in.

For example, double s = 20.7843000,

Cout <setprecision (1) <s <endl; outputs 2e + 001. Because a number is output, only 2.

Cout <setprecision (2) <s <endl; outputs 21.

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

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

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

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

It can be seen that when the end of the decimal part is 0, it cannot be lost!

Showpoint is required for output.

Note:

(If two statements are added after these statements:

Cout <1 <endl;

Cout <1.00800 <endl;

Can I guess what will be output?

Output 1: 1. It is not a float type.

Article 2: 1.008. Take the rule Statement of setprecision (8.

Note:

If a statement exists directly

Int main ()

{

Cout <1 <endl;

Cout <1.00 <endl;

}

Output 1: 1.

The second entry is also: 1. Output by integer
)

Ii. setprecision and showpoint

Syntax: declare cout. setf (ios: showpoint) before the output statement; that's all!

For example, double s = 20.7843000,

Cout. setf (ios: showpoint );

Cout <setprecision (1) <s <endl; will output 2.e+ 001. Note that a "." is added between 2 and e.

Cout <setprecision (2) <s <endl; outputs 21 .. Multiple points!

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

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

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

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

As you can see, the desired data quantity will be output!

Note:

(If two statements are added after these statements:

Cout <1 <endl;

Cout <1.0080 <endl;

Can I guess what will be output?

Output 1: 1. It is not a float type.

The second is 1.0080000. Take the rule Statement of setprecision (8.

 

Iii. setprecision and fixed

If you want to keep a few decimal places, setprecision has to work with fixed !!

Syntax: declare cout. setf (ios: fixed) before the output statement );

For example, 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; will output 20.784.

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

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

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

Note:

(If you add two statements after these statements:

Cout <1 <endl;

Cout <1.008 <endl;

Can I guess what will be output?

Output 1: 1.

Article 2: 1.00800000.

It is the rule statement that undertakes setprecision (8). If it is float, 8 decimal places will be retained. Is it an integer or an integer !)

The statement can also be written as: cout <fixed <setprecision (2) <s <endl;

Even if the following statement is not written <fixed, it will be processed as <fixed.

For example, statements:

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

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

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

All AB statements are processed with 7 reserved digits and 8 decimal digits, instead of 7 or 8 floating point numbers.

If the following statement is c:

Cout <1.008 <endl; also retains 8 decimal places.

Iv. setprecision, showpoint, and fixed

{

Cout <fixed <setprecision (2) <123.456 <endl; // The output result is 123.46.
Cout <showpoint <12345.0006666 <endl; // output 12345.0
Cout <fixed <setprecision (2) <123.456 <endl;

}

For example, double s = 20.7843909

1. statements available

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

Cout <fixed <s <endl; // output 20.78

2. Statements:

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

Cout <showpoint <s <endl; // Output 21. (There is a point)

3. Statements:

Cout <fixed <s <endl; // output 20.78391
Cout <showpoint <s <endl; // output 20.78391
4. Statements:

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

5. Statements:

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