1. Gauss function, rounded down
floor（1.0/4）＝0;
floor（4.0/4）＝1;
floor（5.0/4）＝1;
floor（8.0/4）＝2;
The floor () method is rounded down, similar to the Gaussian function [] in mathematics Get the largest integer not greater than the floating point number. For positive numbers, discard the floating point number part. For complex numbers, discard the floating point number part and then subtract 1
2. ceil function, rounded up.
For example:
ceil（1.0/4）＝1;
ceil（4.0/4）＝1;
ceil（5.0/4）＝2;
ceil（8.0/4）＝2;
The ceil() method is to round up, Double type in parentheses
These two functions are in the math. h library. You can use them directly. IOS does not need to pour the header file again. There are many mathematical functions like this, such as
1. Trigonometric function
double sin (double); Sine
double cos (double); cosine
double tan (double); tangent
2. Inverse trigonometric function
double asin (double); Results between [- PI/2, PI/2]
double acos (double); The result is between [0, PI]
double atan (double); Arctangent (major value), the result is between [- PI/2, PI/2]
double atan2 (double, double); Arctangent (full circle value), the result is between [- PI, PI]
3. Hyperbolic trigonometric function
double sinh (double);
double cosh (double);
double tanh (double);
4. Exponential and logarithmic
double exp (double); Finding the power of natural number e
double sqrt (double); Square root
double log (double); Logarithm with e as the base
double log10 (double); Base 10 logarithm
double pow(double x, double y）; Calculate the y power with x as the base
float powf(float x, float y); The function is the same as that of pow, but the input and output are both floating point numbers
5. Rounding
double ceil (double); Rounded up
double floor (double); Remove the integer
6. Absolute value
double fabs (double); Find absolute value
double cabs(struct complex znum) ; Find the absolute value of complex number
7. Standardized floating point number
double frexp (double f, int *p); Standardized floating point number, f=x * 2 ^ p, if f is known, calculate x, p (x is between [0.5, 1])
double ldexp (double x, int p); Contrary to frexp, if x and p are known, calculate f
8. Rounding and Remaining
double modf (double, double*); The integer part of the parameter is returned through the pointer, and the decimal part is returned
double fmod (double, double); Returns the remainder of the division of two parameters
9. Others
double hypot(double x, double y); Given the length of two right sides of a right triangle, calculate the length of the hypotenuse
double ldexp(double x, int exponent); Calculate x * (the exponential power of 2)
double poly(double x, int degree, double coeffs [] ); Compute Polynomial
int matherr(struct exception *e); Mathematical error calculation processing program
