Mathematical classes in C #, math, floating-point numbers (middle)

mathematical classes in C #, math, floating-point numbers (middle) Preface

Today would not want to write, one is written quite a lot, and then write also remember, but want to go back to the early morning to sleep, tomorrow to learn the car, but this point back to sleep a bit early ah, then write the last one I went back!

Body

And then there's nothing to say, two-week floating-point numbers: float and double are defined in accordance with the Ansi/ieee std754-1985 (which is an IEEE standard for binary floating-point arithmetic).

The float value consists of a 24-bit signed Mantissa and a 8-bit signed exponent. The precision is seven digits after the decimal point. Minimum float value worthy of range and greater than 0:

Float. Minvalue,float. Maxvalue,float. Epsilon

Try to output it yourself to see what the result is.

The double value consists of a 53-bit signed Mantissa and a 11-bit signed exponent with a precision of approximately 16 digits after the decimal point. The range of values and the minimum double value greater than 0:

Double. Minvalue,double. Maxvalue,double. Epsilon

The following code is a floating-point number divided by 0:

float f1=1;

float f2=0;

float f3=f1/f3;

When you see the code above, you may suddenly think of an exception: Dividedbyzeroexception. If these numbers are integers now, they do, but! These are floating-point numbers and do not produce an exception.

In fact, floating-point arithmetic never produces an exception, because F2 is not really 0, it's just a very close to 0 number (how many?). In this case, the F3 equals a special value. It is infinity (positive infinity).

If you change F1 to -1,F3, the result is-infinity (negative infinity).

You can even perform arithmetic operations on infinity, for example, an expression 1/f3 equals 0.

If you change the F1 to 0, that is, 0/infinity, then F3 equals Nan (not a number).

To determine whether a number is infinity or Nan uses a single static method:

BOOL Isinfinity (float fvalue);                      Determine if the infinity is a
bool Ispositiveinfinity (float fvalue);           Judge whether is positive infinity large
bool Isnegativeinfinty (float fvalue);          To determine whether the negative infinity large
bool isNaN (float fvalue);                          To determine whether Nan

The single structure also defines some constant fields

Single.PositiveInfinity.

Single.NegativeInfinity.

Single.nan.

Use C # code output to see

            Console.WriteLine (single.positiveinfinity);
            Console.WriteLine (single.negativeinfinity);
            Console.WriteLine (Single.nan);