Programming Forums > Application Development > C

codylee270 · Dec 4th, 2005, 8:09 PM

Hey everyone,

I wrote a simple C program that asks you to enter a number b/w 1 and 7, and then is displays the day of week corresponding to this number. I.e - you enter 2, you get 'Monday'. Well, i'm thinking the problem is in the function, specifically the way i tried to return day of week. But i'm not really sure so i'm going to post the whole program. It crashes after a number is entered.

(Toggle Plain Text)

#include <stdio.h>
#include <stdlib.h>
char day(int);

int main()
{
    char *week,dayName;
    int n;
    
    printf("Please enter a number between 1 and 7.\n");
    scanf("%d", &n);
    
    while(n<1 || n>7)
    {
           printf("Please retry using a number between 1 and 7.\n");
           scanf("%d", &n);
    }
    
    dayName=day(n);
    printf("The # %d corresponds to %s.\n",n,dayName);
    
    system("PAUSE");
    return 0;
    
}
char day(int n)
{
     n=n-1;
     char *week[]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
     return *week[n];
}

Does anyone see where i went wrong.
Thanks

stevengs · Dec 4th, 2005, 8:40 PM

You are returning a single char. For example, when the user chooses 2, 'M' is returned. printf wants a string and chokes. Change your function declaration and definition as such:

(Toggle Plain Text)

char* day( int n );

.....



char* day( int n );
{
     char *week[] = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };
     return week[ n - 1 ];
}

lectricpharaoh · Dec 4th, 2005, 8:43 PM

What stevengs said. However, you'll also need to make that array inside day() a static one. If you don't, the memory for the array will be reclaimed from the stack when the function exits, and you will be returning a pointer to this newly-unallocated space. This can cause whole heaps of trouble.

codylee270 · Dec 4th, 2005, 9:02 PM

well,
i changed all of that but now it says i have an issue with

(Toggle Plain Text)

dayName=day(n);

says something about "Invalid conversion from 'char*' to 'char'."
What is this?

stevengs · Dec 4th, 2005, 9:10 PM

right, forgot that bit. You declared dayName as a char, but you are assigning to it the char* that is returned from day(). You can drop week, as it is not used anywhere, changing the declaration line to:

(Toggle Plain Text)

char* dayName;

make sure your types match, otherwise you will be relying on implicit conversions which can result in surprises, or the compiler will simply bail.

robrosas · Dec 4th, 2005, 9:15 PM

Just declare dayName as

(Toggle Plain Text)

 char* dayName;

robrosas · Dec 4th, 2005, 9:17 PM

Ooops sorry didnt grabbed that last post...

Kaja Fumei · Dec 4th, 2005, 9:20 PM

Since * in variable declarations are bound to the variable name and not the base type, this line:

(Toggle Plain Text)

char *week,dayName;

makes week a char* and dayName a char. So change that line to:

(Toggle Plain Text)

char *week, *dayName;

codylee270 · Dec 4th, 2005, 9:28 PM

Great, makes sense, and works wonderful.. Thanks..

Dec 4th, 2005, 8:09 PM	#1
codylee270 Unverified User Join Date: Sep 2005 Posts: 209 Rep Power: 0	simple pointer array w/ function crash Hey everyone, I wrote a simple C program that asks you to enter a number b/w 1 and 7, and then is displays the day of week corresponding to this number. I.e - you enter 2, you get 'Monday'. Well, i'm thinking the problem is in the function, specifically the way i tried to return day of week. But i'm not really sure so i'm going to post the whole program. It crashes after a number is entered. (Toggle Plain Text) #include <stdio.h> #include <stdlib.h> char day(int); int main() { char week,dayName; int n; printf("Please enter a number between 1 and 7.\n"); scanf("%d", &n); while(n<1 \|\| n>7) { printf("Please retry using a number between 1 and 7.\n"); scanf("%d", &n); } dayName=day(n); printf("The # %d corresponds to %s.\n",n,dayName); system("PAUSE"); return 0; } char day(int n) { n=n-1; char week[]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"}; return week[n]; } #include <stdio.h> #include <stdlib.h> char day(int); int main() { char week,dayName; int n; printf("Please enter a number between 1 and 7.\n"); scanf("%d", &n); while(n<1 \|\| n>7) { printf("Please retry using a number between 1 and 7.\n"); scanf("%d", &n); } dayName=day(n); printf("The # %d corresponds to %s.\n",n,dayName); system("PAUSE"); return 0; } char day(int n) { n=n-1; char week[]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"}; return week[n]; } Does anyone see where i went wrong. Thanks

Dec 4th, 2005, 8:40 PM	#2
stevengs Professional Programmer Join Date: May 2005 Location: Bad Nauheim, Germany Posts: 436 Rep Power: 4	You are returning a single char. For example, when the user chooses 2, 'M' is returned. printf wants a string and chokes. Change your function declaration and definition as such: (Toggle Plain Text) char* day( int n ); ..... char* day( int n ); { char week[] = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" }; return week[ n - 1 ]; } char day( int n ); ..... char* day( int n ); { char *week[] = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" }; return week[ n - 1 ]; } __________________ -Steven "Is this a piece of your brain?" - Basil Fawlty

Dec 4th, 2005, 8:43 PM	#3
lectricpharaoh SEXY SHOELESS GOD OF WAR! Join Date: Jun 2005 Location: Wet west coast of Canada Posts: 1,183 Rep Power: 5	What stevengs said. However, you'll also need to make that array inside day() a static one. If you don't, the memory for the array will be reclaimed from the stack when the function exits, and you will be returning a pointer to this newly-unallocated space. This can cause whole heaps of trouble. __________________ And once again, Probability proves itself willing to sneak into a back alley and service Drama as would a copper-piece harlot. - Vaarsuvius, Order of the Stick

Dec 4th, 2005, 9:02 PM	#4
codylee270 Unverified User Join Date: Sep 2005 Posts: 209 Rep Power: 0	well, i changed all of that but now it says i have an issue with (Toggle Plain Text) dayName=day(n); dayName=day(n); says something about "Invalid conversion from 'char*' to 'char'." What is this?

Dec 4th, 2005, 9:10 PM	#5
stevengs Professional Programmer Join Date: May 2005 Location: Bad Nauheim, Germany Posts: 436 Rep Power: 4	right, forgot that bit. You declared dayName as a char, but you are assigning to it the char* that is returned from day(). You can drop week, as it is not used anywhere, changing the declaration line to: (Toggle Plain Text) char* dayName; char* dayName; make sure your types match, otherwise you will be relying on implicit conversions which can result in surprises, or the compiler will simply bail. __________________ -Steven "Is this a piece of your brain?" - Basil Fawlty

Dec 4th, 2005, 9:15 PM	#6
robrosas Newbie Join Date: Nov 2005 Location: Puerto Rico Posts: 12 Rep Power: 0	.... Just declare dayName as (Toggle Plain Text) char* dayName; char* dayName; __________________ From P.R. to the World!! RoBeRt

Dec 4th, 2005, 9:17 PM	#7
robrosas Newbie Join Date: Nov 2005 Location: Puerto Rico Posts: 12 Rep Power: 0	Ooops sorry didnt grabbed that last post... __________________ From P.R. to the World!! RoBeRt

Dec 4th, 2005, 9:20 PM	#8
Kaja Fumei Hobbyist Programmer Join Date: Oct 2005 Posts: 134 Rep Power: 4	Since * in variable declarations are bound to the variable name and not the base type, this line: (Toggle Plain Text) char week,dayName; char week,dayName; makes week a char* and dayName a char. So change that line to: (Toggle Plain Text) char week, dayName; char week, dayName;

Dec 4th, 2005, 9:28 PM	#9
codylee270 Unverified User Join Date: Sep 2005 Posts: 209 Rep Power: 0	Great, makes sense, and works wonderful.. Thanks..

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Programming Forums > Application Development > C

simple pointer array w/ function crash