Reading in data from Text file

**fortune2k** · 04-03-2008

lol my instructer will say look at the lecture notes and well theres nothing on there bout what im stuck on lol i aint the best at C but its giving me headaches but im gonna try figure this out

**fortune2k** · 04-03-2008

right i have managed to get it to put out an error message but having problems with if its true setting the point for the places.

i decided to use flag as a int and set it to 1 or 0.

this is what i have

Code:

         wrong=0;  
                    scanf("&#37;16s", pos[i]);
                          size_t x;  
                          flag = 0;
                          for(x = 0; x < sizeof(cities) / sizeof(*cities); x ++) 
                            {
                              if(!strcmp(cities[x], pos[i])==0){point[i] = x;} // assigns point a number depends what place name was enterd  
                              else {flag=1;}    
                            }
                            if(flag==0)
                            {
                               printf("\n Invalid place name please re enter: ");
                               i--;
                               wrong=1;       
                            }

output :
http://i57.photobucket.com/albums/g230/fortune2k/dd.jpg

**Elysia** · 04-03-2008

You should get yourself a debugger. Perhaps Visual Studio.
And note that this line

Code:

 if(!strcmp(cities[x], pos[i])==0){point[i] = x;}

Looks suspicious.
Strcmp returns 0 if the strings match. Yet the "!" operator inverses the result so if strcmp returns 1, it will be changed to 0 before the comparison. Likewise, if it returns 0 or < 0, it will be 1 before the compare. Watch out.

**fortune2k** · 04-03-2008

im using dev c++ maybe i should change sooo what shall i change it to then i tryed !=0 and taking it out completly and well it doesnt work

**Elysia** · 04-03-2008

Code:

if(strcmp(cities[x], pos[i])==0){point[i] = x;}

Remove the "!".
Strcmp returns 0 if the strings are equal.
I suggest you get a debugger and learn basic debugging facilities. Stepping through code and checking the value of variables.
Basic stuff. There will come a day when you need a debugger.,

**vart** · 04-03-2008

Likewise, if it returns 0 or < 0, it will be 1

How is it so?

Code:

#include<stdio.h>
int main() 
{
    printf("&#37;d %d %d\n", !(-1), !0 , !1);
    return 0;
}

output

Code:

0 1 0

**Elysia** · 04-03-2008

That's what I get for not testing

I assumed since < 0 will result in false, reversing the value will turn it "true."
Well, that goes to show that using ! can be dangerous if not used properly.

**vart** · 04-03-2008

values that are < 0 as well as the values that are >0 all evaluate to true

**fortune2k** · 04-03-2008

ok uve confused me now

**Elysia** · 04-03-2008

Originally Posted by vart

values that are < 0 as well as the values that are >0 all evaluate to true

Brain error!

The area in the brain where the information was stored has been short circuited, so it fell back on trying to guess with the information it had which obviously turned out wrong!

Fortune: Don't use !strcmp, just do strcmp and compare to 0 to see if the strings match.

**vart** · 04-03-2008

Originally Posted by fortune2k

ok uve confused me now

What exactly?
in C:
0 - is false
all other values - are true

**fortune2k** · 04-03-2008

yes i understand that i mean how to have it set in the if statement

**vart** · 04-03-2008

Originally Posted by fortune2k

yes i understand that i mean how to have it set in the if statement

you do not need it here

Code:

if(strcmp(...) == 0)
{
   /* strings match */
}

or

Code:

if(strcmp(...) != 0)
{
   /* strings do not match */
}

depending on what you need

**fortune2k** · 04-03-2008

Originally Posted by vart

you do not need it here

Code:

if(strcmp(...) == 0)
{
   /* strings match */
}

or

Code:

if(strcmp(...) != 0)
{
   /* strings do not match */
}

depending on what you need

right this is what i have

Code:

   scanf("%16s", pos[i]);
                          size_t x;  
                          flag = 0;
                          for(x = 0; x < sizeof(cities) / sizeof(*cities); x ++) 
                            {
                              if(!strcmp(cities[x], pos[i])==0){point[i] = x;} // assigns point a number depends what place name was enterd  
                              else if(!strcmp(cities[x], pos[i])!=0) {flag=1;}    
                            }
                            if(flag==0)
                            {
                               printf("\n Invalid place name please re enter: ");
                               i--;
                               wrong=1;       
                            }

i still get no distance output its still the same as

http://i57.photobucket.com/albums/g230/fortune2k/dd.jpg