"C language" deep entry rounding & four functions

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Preface

integer

⒈trunc － 0 Round to

⒉floor － Floor rounding

⒊ceil－ Infinite rounding

⒋round－ rounding

Preface

This blog will give you an in-depth understanding of what rounding is . I mentioned " depth " You can see that this article is still very detailed in explaining rounding, and there must be some knowledge points in it , But don't think that depth is to design many difficult knowledge points . In fact, they are all relatively easy knowledge points , Then don't talk too much nonsense and get to the point

integer

About " integer " It seems that we are both familiar with and unfamiliar with this word , Familiar because we often use rounding when programming . Strangeness is because I haven't thoroughly understood this rounding , Next, let's focus on rounding as a discussion .

integer ⇢ Rounding literally means very easy to understand, which is nothing more than rounding an integer 2.5 It is a floating-point number. If we round it, it is 2 The integer of . The code example is as follows ↓

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main(void)
{
	int a = 2.99;
	int b = -2.99;
	printf("a=%2d\n", a);
	printf("b=%2d\n", b);
	return 0;
}

Running results

a =  2

b = -2

explain ⇢ In the above code, we can know that it is not according to our mathematical rounding, but no matter how many decimal places you have , This is also the reason why I take the decimal point of the variable as big as possible, that is, I want you to understand this concept very intuitively . In a word : The number after the decimal point is omitted directly .

summary ⇢「C Language 」 Rounding defaults to "0 Round to ".

⒈trunc － 0 Round to

trunc  The header file for is ⇢ #include<math.h>

Expand your knowledge ⇢ about 「C Language 」 In fact, it has a rounding function. I believe many friends don't know 「C Language 」 To have this trunc Rounding function .

trunc  The parameters are as follows ↓

     double trunc  (     double x);
      float truncf (      float x);
long double truncl (long double x);

The code example is as follows ↓

#include<stdio.h>
#include<math.h>
int main(void)
{
	printf("%2f\n", trunc(2.99));
	printf("%2f\n", trunc(-2.99));
	printf("%2d\n", (int)trunc(2.99));
	printf("%2d\n", (int)trunc(-2.99));
	return 0;
}

Running results

 2

-2

 2

-2

notes ⇢ Here we need to note that the return value of the function is of floating-point type , If you use plastic printing, you need to strongly convert the type to (int)

explain ⇢ stay C The default language is 0 To round up .

⒉floor － Floor rounding

floor  The header file for is ⇢ #include<math.h>

floor  The parameters are as follows ↓

double floor (double x);

The code example is as follows ↓

#include<stdio.h>
#include<math.h>
int main(void)
{
	printf("%2d\n", (int)floor(2.99));
	printf("%2d\n", (int)floor(-2.99));
	printf("%2d\n", (int)floor(2.99));
	printf("%2d\n", (int)floor(-2.99));
	return 0;
}

Running results

 2

-3

 2

-3

notes ⇢ We need to remember that it's going to -∞ Close in the middle , From the running results of the above code, I believe you can also see that it is all the same -∞ Close in the middle .

⒊ceil－ Infinite rounding

ceil The header file for is ⇢ #include<math.h>

ceil  The parameters are as follows ↓

double ceil (double x);

The code example is as follows ↓

#include<stdio.h>
#include<math.h>
int main(void)
{
	printf("%2d\n", (int)ceil(2.99));
	printf("%2d\n", (int)ceil(-2.99));
	printf("%2d\n", (int)ceil(2.99));
	printf("%2d\n", (int)ceil(-2.99));
	return 0;
}

Running results

 3

-2

 3

-2

notes ⇢ We need to remember that it goes +∞ Close in the middle , From the running results of the above code, I believe you can also see that it is all the same +∞ Close in the middle .

⒋round－ rounding

round The header file for is ⇢ #include<math.h>

round  The parameters are as follows ↓

     double round  (double x);
      float roundf (float x);
long double roundl (long double x);

The code example is as follows ↓

#include<stdio.h>
#include<math.h>
int main(void)
{
	printf("%2d\n", (int)round(2.99));
	printf("%2d\n", (int)round(-2.01));
	printf("%2d\n", (int)round(2.01));
	printf("%2d\n", (int)round(-2.99));
	return 0;
}

Running results

 3

-3

 2

-3

notes ⇢ This is the way of rounding in our mathematics .

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summary － The final choice depends on your application scenario ～

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