Summary of C-language rounding method

the C language has the following rounding methods:1. Direct assignment to integer variablesint I = 3.5; or i = (int) 3.5;

This approach employs a fractional portion.

2, Integer division operator '/' rounding

the '/' itself has a rounding function (Int/int), but integer division is related to the rounding result of negative numbers and the C compiler used.

3. Using the floor function

Floor (x) returns the largest integer that is less than or equal to X . Such as:

Floor (3.5) = 3

Floor (-3.5) =-4

4. Using the Ceil function

ceil (x) returns the smallest integer greater than x . Such as:

ceil (3.5) = 4

Ceil (-3.5) = 3

Floor () is rounded to negative infinity , floor (-3.5) =-4;

ceil () is rounded to positive infinity , ceil (-3.5) =-3.

But in c the Ceil and floor () functions are returned as double types .

5. Rounding up Method

A simple upward rounding method is found on the Internet;

Here we use <> for rounding up, [] for rounding down, we can prove that:

<n/m>= [(N-1)/m]+1 (0 < M <= N m,n∈z)

without losing its generality, we set n = mk+r (0 <= R < m,k∈z),

(1) when R > 0 o'clock,

Left:<n/m> = < (mk+r)/M >= <k+r/m>= k+<r/m> = k+1

Right: [(N-1)/m]+1 = [(mk+r-1)/m]+1 = [k + (r-1)/m]+1 = k+1+[(r-1)/m]=k+1

(2) when r = 0 o'clock,

Left:<n/m> = k

Right:

[(N-1)/m]+1 = [(Mk-1)/m]+1 = [(M (k-1) +m-1)/m]+1

= [k-1+ (M-1)/m]+1 = k+[(M-1)/M]

= k

In conclusion, the proposition is to be proven.

with this formula, we can calculate this in the code:

int nn = (N-1)/M +1

the "/" in the formula is rounded down.

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Summary of C-language rounding method