The last few errors in my first program!

**krazymanrebirth** · 09-14-2009

Hey first of all, first post! I think this community is a great place for learning, i cant wait to start helping you guys when i get up to par

Anyways... This program i made defines a triangle in very basic ways... Basically its giving me 2 problems, one is that if i type in a letter... the program goes haywire.
The other problem is that my area pops up twice on 2 on equilateral and scalene... I believe this is because of my else statement for isosceles
Thanks again

Code:

#include <stdio.h>
#include <math.h>

int main(void)
{
/** Declaring Integers **/

    float sidea, sideb, sidec, s, area;
    char y, n, loop, trash, loop2;
    y=1;
    n=0;
/** While clause**/
    do
    {
/**Enter Sides of Triangle**/

    printf( "Enter Side A:" );
    scanf( "%f", &sidea);
    printf( "Enter Side B:" );
    scanf( "%f", &sideb);
    printf( "Enter Side C:" );
    scanf( "%f, %c", &sidec);
    trash = getchar();
/** Error Checking**/
   
/**Imposible Triangle**/
    if ((sidea + sideb <= sidec) || (sideb + sidec <= sideb) || (sidea +sideb <= sidec))
    {
        printf( "Triangle is impossible\n" );
    }

/**Equilateral Triangle**/
    else if ((sidea == sideb) && (sidea == sidec) && (sideb == sidec))
    {
        printf( "Triangle is Equilateral\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "%6.2f", area);
    }

/**Scalene Triangle**/
    else if ((sidea != sideb) && (sidea != sidec) && (sideb != sidec))
    {
        printf( "Triangle is Scalene\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "%6.2f", area);
    }

/**Isosceles**/
    else printf( "Triangle is Isosceles\n" );
    {
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "%6.2f", area);
    }
/**Loop**/
   
    do
    {
    loop2=0;
    printf( "Would you like to create another triangle? (Y/N)\n" );
    scanf( "%c, %c", &loop);
    getchar();
    if ((loop == 'y') || (loop == 'Y'))
    loop=y;
    else if ((loop == 'n') || (loop == 'N'))
    loop=n;
    else ((printf ("Please enter either (Y/N)\n"))&& (loop2=1));
    }
    while (loop2==1);
    }

    /*close of do loop*/
   
while(loop == y);
   
return 0;
}

**Dino** · 09-14-2009

Here's a logic error:

Code:

if ((sidea + sideb <= sidec) || (sideb + sidec <= sideb) || (sidea +sideb <= sidec))

Here's a redundant test:

Code:

/**Equilateral Triangle**/
    else if ((sidea == sideb) && (sidea == sidec) && (sideb == sidec))

One too many %c.

Code:

    printf( "Would you like to create another triangle? (Y/N)\n" );
    scanf( "%c, %c", &loop);

**MK27** · 09-14-2009

"haywire" may seem descriptive, but in the case of a programming error, it is kind of the opposite. In any case, it is not really surprising that a letter is not well absorbed as a floating point number, I think you are aware of that. To circumvent the problem, you must perform some "input validation". But don't worry about that quite yet.

Letters, and anything else that counts as a char, do have an integer value, known as the "ascii value".

ASCII Table / Extended ASCII Codes

"Anything else" here includes the newline, aka '\n', with a value of 10 in the ascii table. Most likely, your problem is because at certain points you use scanf("%c"). What the user enters in such a case is not one character, but two, the second one being '\n' from the ENTER key. That character is left in the input buffer, and is absorbed by the next scanf() call.

Here are some ways to deal with that:

alternative for fflush(stdin)

Do not use fflush(stdin), obviously.

**Adak** · 09-14-2009

We just had this same program, and sorted it out last week. Search for "triangle" in the body of the post.

You have the same errors, almost.

Then, as now, you can't scanf() a float and a char, and somehow put it into just one variable.

I'd avoid turning this program in as yours. Make some other changes to it (although you can't change the equation basics).

If side a == side b, and side a == side c, you don't have to check if side b == side c for an equilateral triangle. That's a given.

**krazymanrebirth** · 09-14-2009

thanks

that actually fixed about everything. I want to read more on the ASCII values i think its intriguing!

anyways, I'm not sure if you guys are willing to find any other errors in my program. I know the area comes out twice when i work on an equilateral or scalene triangle... Is that because of my else statement with Iscosceles?

Also it spits out an area when I am working with impossible triangles (when i thought i never told it to???)
Thanks again ahead of time
-James

PS: Adak i cant find the post your talking about

Could i get a link?

Code:

#include <stdio.h>
#include <math.h>

int main(void)
{
/** Declaring Integers **/

    float sidea, sideb, sidec, s, area;
    char y, n, loop, trash, loop2;
    y=1;
    n=0;
/** While clause**/
    do
    {
/**Enter Sides of Triangle**/

    printf( "Enter Side A:" );
    scanf( "%f", &sidea);
    printf( "Enter Side B:" );
    scanf( "%f", &sideb);
    printf( "Enter Side C:" );
    scanf( "%f, %c", &sidec);
    trash = getchar();
/** Error Checking**/
   
/**Imposible Triangle**/
    if ((sidea + sideb <= sidec) || (sideb + sidec <= sideb) || (sidea + sidec <= sideb))
    {
        printf( "Triangle is impossible\n" );
    }

/**Equilateral Triangle**/
    else if ((sidea == sideb) && (sidea == sidec))
    {
        printf( "Triangle is Equilateral\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "%6.2f", area);
    }

/**Scalene Triangle**/
    else if ((sidea != sideb) && (sidea != sidec) && (sideb != sidec))
    {
        printf( "Triangle is Scalene\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "%6.2f", area);
    }

/**Isosceles**/
    else printf( "Triangle is Isosceles\n" );
    {
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "%6.2f", area);
    }
/**Loop**/
   
    do
    {
    loop2=0;
    printf( "Would you like to create another triangle? (Y/N)\n" );
    scanf( "%c", &loop);
    getchar();
    if ((loop == 'y') || (loop == 'Y'))
    loop=y;
    else if ((loop == 'n') || (loop == 'N'))
    loop=n;
    else ((printf ("Please enter either (Y/N)\n"))&& (loop2=1));
    }
    while (loop2==1);
    }

    /*close of do loop*/
   
while(loop == y);
   
return 0;
}

**krazymanrebirth** · 09-14-2009

fixed it, thanks anyways ^_^

**MK27** · 09-14-2009

Hey, sorry, I just noticed you did do this:

Code:

scanf( "%f", &sidec);
trash = getchar();

so sorry for needlessly filling you in on something you already know.

Your problem is this:

Code:

/**Isosceles**/
    else printf( "Triangle is Isosceles\n" );
    {
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "%6.2f", area);
    }

the printf should be inside the block -- as is, the block is not part of the if/else if /else and always executed.

**krazymanrebirth** · 09-14-2009

hmm this is what i did to fix it. Just changed it from an else to an else if.

Code:

/**Isosceles**/
    else if ((sidea == sideb) || (sidea == sidec) || (sideb == sidec))
    {
        printf( "Triangle is Isosceles\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "Squareroot is:%6.2f\n", area);
    }

Also here is my finished code, If anyone wants to learn from it go ahead thats why its there

also..Is this an A in my lab by all your standards? My tabbing etc is readable? integers make sense? ^_^ thanks

Code:

#include <stdio.h>
#include <math.h>

int main(void)
{
/** Declaring Integers **/

    float sidea, sideb, sidec, s, area;
    char y, n, loop, trash, loop2;
    y=1;
    n=0;
/** While clause**/
    do
    {
/**Header**/
    printf( "Welcome to the Triangle Calculator, Please enter the sides of the triangle:\n" );
    printf( "---------------------------------------------------------------------------\n" );
/**Enter Sides of Triangle**/

    printf( "Enter Side A:" );
    scanf( "%f", &sidea);
    printf( "Enter Side B:" );
    scanf( "%f", &sideb);
    printf( "Enter Side C:" );
    scanf( "%f, %c", &sidec);
    trash = getchar();
/** Error Checking**/
    
/**Imposible Triangle**/
    if ((sidea + sideb <= sidec) || (sideb + sidec <= sideb) || (sidea + sidec <= sideb))
    {
        printf( "Triangle is impossible\n" );
    }

/**Equilateral Triangle**/
    else if ((sidea == sideb) && (sidea == sidec))
    {
        printf( "Triangle is Equilateral\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "Squareroot is:%6.2f\n", area);
    }

/**Scalene Triangle**/
    else if ((sidea != sideb) && (sidea != sidec) && (sideb != sidec))
    {
        printf( "Triangle is Scalene\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "Squareroot is:%6.2f\n", area);
    }

/**Isosceles**/
    else if ((sidea == sideb) || (sidea == sidec) || (sideb == sidec))
    {
        printf( "Triangle is Isosceles\n" );
        s = (sidea + sideb + sidec)/2;
        area=sqrt(s*(s-sidea)*(s-sideb)*(s-sidec));
        printf( "Squareroot is:%6.2f\n", area);
    }
/**Loop**/
    
    do
    {
    loop2=0;
    printf( "Would you like to create another triangle? (Y/N)\n" );
    scanf( "%c", &loop);
    getchar();
    if ((loop == 'y') || (loop == 'Y'))
    loop=y;
    else if ((loop == 'n') || (loop == 'N'))
    loop=n;
    else ((printf ("Please enter either (Y/N)\n"))&& (loop2=1));
    }
    while (loop2==1);
    }

    /*close of do loop*/
    
while(loop == y);
    printf( "Thank you come again -- Program Created By: James Goetz\n" );
return 0;
}

**krazymanrebirth** · 09-14-2009

AH dammit! when you put a letter instead of a number (for any side variable) it throws it into an infinite loop! Can anyone tell me what im missing here

**MK27** · 09-14-2009

If that is a criteria of your assignment, you will have to write a validation function that simply takes input as a string, using fgets(), then you can validate the string and get data from it in the way you are now but using sscanf().

**krazymanrebirth** · 09-14-2009

hmm, we havent learned fgets() yet, We just learned loops in our C book (C by discovery)

I'm all for learning so im reading up on the fgets() now... but would there be any other way?

thanks again MK27 your awesome

**MK27** · 09-14-2009

Originally Posted by krazymanrebirth

I'm all for learning so im reading up on the fgets() now... but would there be any other way?

Yes, you can check the return value of scanf(). Here is a clue:

Code:

if (!(scanf( "%f", &sidea))) puts("!NaN!");

put that in and figure out how to make it happen.

**krazymanrebirth** · 09-14-2009

Im sorta lost on where to put it, But I tried.. and failed...

Code:

/**Imposible Triangle**/
    if ((sidea + sideb <= sidec) || (sideb + sidec <= sideb) || (sidea + sidec <= sideb))
    {
        if (!(scanf( "%f", &sidea)))
        printf( "Triangle is impossible\n" );
    }

**MK27** · 09-14-2009

Originally Posted by krazymanrebirth

Im sorta lost on where to put it, But I tried.. and failed...

yeah. maybe I should have said "replace one of the scanf lines" instead of "put this in".

The problem is scanf is not reading anything when you enter a letter, so you end up with an undefined value in one of your floats, which you feed to sqrt().

**krazymanrebirth** · 09-14-2009

Im not understanding the mathematics (or coding explanation) for what the
if (!(scanf( "%f", &sidea))) puts("!NaN!");
does... I mean i understand your explanation at least ^_^

So turning these into if statements... I dont understand that or the puts("!NaN!") << not a number??

/**Enter Sides of Triangle**/

printf( "Enter Side A:" );
if (!(scanf( "%f", &sidea))) puts("!NaN!");
printf( "Enter Side B:" );
if (!(scanf( "%f", &sideb))) puts("!NaN!");
printf( "Enter Side C:" );
if (!(scanf( "%f", &sidec))) puts("!NaN!");
trash = getchar();

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