I copy some C code from the textbook, but when I run gcc -o triangle triangle.c, I get errors ``` triangle.c: In function 'main': triangle.c:23:8: error: expected ')' before '{' token { ^ triangle.c:32:5: error: expected expression before '}' token } ^ ``` here is the original code ``` #include #include #define EPS 1e-1 int main() { float a,b,c; int flag = 1; printf("Input a,b,c:"); scanf("%f,%f,%f",&a,&b,&c); if (a+b>c && b+c>a && a+c>b) { if (fabs(a-b)

@"unicorn"#p14714 can you try this ? fabs(c*c+b*b-a*a

I get errors when gcc -o hanoi hanoi.c, its code is game of Tower of Hanoi ``` ld: /tmp//ccHAVPp3.o: in function `main': hanoi.c:(.text+0x56): undefined reference to `Hanoi' ld: /tmp//ccHAVPp3.o: in function `hanoi': hanoi.c:(.text+0xaa): undefined reference to `Hanoi' ld: hanoi.c:(.text+0xd7): undefined reference to `Hanoi' ``` original code ``` #include void Hanoi (int n,char a,char b,char c); void Move (int n,char a,char b); int main() { int n; printf("Input the number of disks:"); scanf("%d", &n); printf("Steps of moving %d disks from A to B by means of C:\n", n); Hanoi(n, 'A', 'B' , 'C' ); return 0; } void hanoi(int n, char a, char b, char c) { if (n == 1) { Move(n, a, b); } else { Hanoi(n-1, a, c, b); Move(n, a, b); Hanoi(n-1, c, b, a); } } void Move (int n, char a, char b) { printf("Move %d: from %c to %c\n",n, a,b); } ```

@"unicorn"#p14723 Line 13: `void hanoi(...` => `void Hanoi(...`

`gets()` unsafe, how to replace `gets()`? `gcc -o sort sort.c` ``` ld: /tmp//cc4m3WzB.o: in function `main': sort.c:(.text+0x9b): warning: warning: this program uses gets(), which is unsafe. ``` original code ``` #include #include #define MAX_LEN 10 #define N 150 void SortString(char str[][MAX_LEN],int n); int main() { int i,n; char name[N][MAX_LEN]; printf("How many countries?"); scanf("%d",&n); getchar(); printf("Input their names:\n"); for (i=0;i

please point out mistake of the C code

nia

Missing ) on line above line that prints "zhijiao"

unicorn

nia
you mean that line should be like this? I correct print to printf

printf("zhijiao"))

I get more errors.

I copy the code exactly from the textbook, I think the code should be fine, but why I get errors using gcc?

unicorn

the error said line 23 and line 32
line 23 is line before
printf("zhijiao");
line 32 is line next
printf("sanjiaoxing\n");

line 22 has a pair of (), why still need )?
line 32's }and line 11'{ is a pair, why need expression before }?

Jay

unicorn can you try this ?

fabs(cc+bb-aa<=EPS) convert it to fabs(cc+bb-aa)<=EPS

unicorn

thanks, it works

unicorn

I get errors when gcc -o hanoi hanoi.c, its code is game of Tower of Hanoi

ld: /tmp//ccHAVPp3.o: in function `main':
hanoi.c:(.text+0x56): undefined reference to `Hanoi'
ld: /tmp//ccHAVPp3.o: in function `hanoi':
hanoi.c:(.text+0xaa): undefined reference to `Hanoi'
ld: hanoi.c:(.text+0xd7): undefined reference to `Hanoi'

original code

#include<stdio.h>
void Hanoi (int n,char a,char b,char c);
void Move (int n,char a,char b);
int main()
{     
    int n;  
    printf("Input the number of disks:");
    scanf("%d", &n);
    printf("Steps of moving %d disks from A to B by means of C:\n", n);
    Hanoi(n, 'A', 'B' , 'C' );
    return 0;
}    
    void hanoi(int n, char a, char b, char c) 
{    
    if (n == 1)
    {
       Move(n, a, b);
    }
    else    
    {
        Hanoi(n-1, a, c, b);
        Move(n, a, b);
        Hanoi(n-1, c, b, a);
    }
}    
    void Move (int n, char a, char b) 
    {
         printf("Move %d: from %c to %c\n",n, a,b);
    }

rvp

unicorn Line 13: void hanoi(... => void Hanoi(...

wravoc

Is this actually from a Chinese Textbook on Computer Programming? Can you link it for us? Such an obvious error. Check the book for an errata section where you can go online and get the corrections for any errors in the book.

What level of education is it for?

unicorn

wravoc
It's not from a book, it's from a class. The book is for university students.
I can't find mistakes sometimes so I put it here.

unicorn

gets() unsafe, how to replace gets()? gcc -o sort sort.c

ld: /tmp//cc4m3WzB.o: in function `main':
sort.c:(.text+0x9b): warning: warning: this program uses gets(), which is unsafe.

original code

#include<stdio.h>
#include<string.h>
#define MAX_LEN 10
#define N 150
void SortString(char str[][MAX_LEN],int n);
int main()
{
    int i,n;
    char name[N][MAX_LEN];
    printf("How many countries?");
    scanf("%d",&n);
    getchar();
    printf("Input their names:\n");
    for (i=0;i<n;i++)
    {
        gets(name[i]);
    }
    SortString(name,n);
    printf("Sorted results:\n");
    for (i=0;i<n;i++)
    {
        puts(name[i]);
    }
    return 0;
}
void SortString(char str[][MAX_LEN],int n)
{
    int i,j;
    char temp[MAX_LEN];
    for (i=0;i<n-1;i++)
    {
        for (j=i+1;j<n;j++)
        {
            if (strcmp(str[j],str[i])<0)
            {
               strcpy(temp,str[i]);
               strcpy(str[i],str[j]);
               strcpy(str[j],temp);
            }
        }
    }
}

I changed gets() to fgets(name[i],sizeof(name),stdin), I get a result

unicorn$ ./sort
How many countries?5
Input their names:
America
England
Australia
Sweden
Finland
Sorted results:
America

Australia
England

England

Finland

Sweden

if I change gets()to fgets(name[i],sizeof(name[i]),stdin), the result is

unicorn$ ./sort
How many countries?5
Input their names:
America
England
Australia
Sweden
Sorted results:


America

Australia
England

Sweden

result of the original code should be

How many countries?5
Input their names:
America
England
Australia
Sweden
Finland
Sorted results:
America
Australia
England
Finland
Sweden

rvp

unicorn fgets also stores the EOL chars.: \n, `\r\n', '\r'. So,

Increase MAX_LEN (Australia\n\0 occupies 11 chars)
Either strip the EOL chars. or don't add any more: puts(name[i] => printf("%s", name[i])

unicorn

rvp
I increase MAX_LEN to 20, here is the result I get

unicorn$ ./sort
How many countries?5
Input their names:
America
England
Australia
Sweden
Finland
Sorted results:
America

Australia

England

Finland

Sweden

How to remove blank lines after each word?

rvp

unicorn See point #2, above. Or, use this getln() function instead of fgets():

#include <stdio.h>
#include <string.h>

/**
 * Get a line; strip Unix and MS-DOS EOL chars.
 */
static char*
getln(char* buf, int sz)
{
	size_t n;

	if (fgets(buf, sz, stdin) == NULL)
		return NULL;
	n = strlen(buf);
	if (n && buf[n - 1] == '\n')
		buf[--n] = '\0';
	if (n && buf[n - 1] == '\r')
		buf[--n] = '\0';
	return buf;
}

int
main(void)
{
	char buf[BUFSIZ];

	while (getln(buf, sizeof buf) != NULL)
		printf("%s\n", buf);
	return 0;
}