C program that displays shapes. Keep getting errors.

graemef · 10-10-2010, 09:20 PM

Quote:

Originally Posted by boilers969

My goal is to have the program keep running and never terminate unless a user enters a char other than s,h,f.

Okay with that in mind don't worry about drawing the shapes yet but concentrate on the s,h,f terminate functionality. Starting with this segment of code that you already have:

Code:

#include<stdio.h>

int main()
{
   while(1)
   {
      char shape=1;
      int row;
      printf("Enter shape type (s/h/f):");
      scanf("%c",&shape);
      printf("Enter shape length: ");
      scanf("%d",&row);
      if(row<=0)
         printf("Shape length cannot be negative. Try again\n");
   }
}

Can you modify this code to achieve your first goal?

boilers969 · 10-10-2010, 09:37 PM

Would something like this work?

Code:

#include<stdio.h>

int main()
{
   while(1)
   {
      char shape=1;
      int row;
      printf("Enter shape type (s/h/f):");
      scanf("%c",&shape);
      printf("Enter shape length: ");
      scanf("%d",&row);
      if(row<=0)
         printf("Shape length cannot be negative. Try again\n");
      if(shape!=s/h/f)
         then terminate the program(i dont know the command to terminate it)
   }
}

sag47 · 10-10-2010, 10:07 PM

You had it before:

Code:

#include<stdio.h>

int main()
{
   while(1)
   {
      char shape=1;
      int row;
      printf("Enter shape type (s/h/f):");
      scanf("%c",&shape);
      printf("Enter shape length: ");
      scanf("%d",&row);
      if(row<=0)
         printf("Shape length cannot be negative. Try again\n");
      if(shape!=s/h/f)
         return 0;
   }
}

graemef · 10-10-2010, 10:09 PM

First I would restructure it a little. Check that a valid option has been entered s, h or f before asking for the length.

Second the if conditional needs to be broken down into three parts: is it a 's' or is it a 'h' or is it a 'f'. Often it is easier to consider the positive outcome (was a valid value entered) rather that the negative outcome (was an invalid value entered). The negative outcome will be part of the else statement.

To exit from the program you can use the return statement.

boilers969 · 10-10-2010, 10:10 PM

So looking at the next goal. I want to output something for what they input. So is it alright to use 3 different switch statements?

boilers969 · 10-10-2010, 11:25 PM

So looking at the next goal. I want to output something for what they input. So is it alright to use 3 different switch statements?

graemef · 10-10-2010, 11:29 PM

Use a single switch statement with three case statements one for each legal input value. The default case will indicate an invalid value.

If you think carefully about it the switch statement actually means that you can throw away the if statement.

boilers969 · 10-10-2010, 11:30 PM

Ok this is where I get confused. I had it as a single switch statement and then changed it. I thought you could only do a switch on one variable?

graemef · 10-10-2010, 11:38 PM

you can only do a switch on one variable but you will have different case statements for each value that variable can take.

For example:

Code:

switch( i ) 
{
    case -1:
        n++;
        break;
    case 0 :
        z++;
        break;
    case 1 :
        p++;
        break;
}

gratuitously copied from here.

boilers969 · 10-10-2010, 11:41 PM

So in my case would this work? Except of course I will have to add more.

Code:

switch(shape)
{
case s;
   break;
case h;
   break;
case f;
   break;
}

sag47 · 10-11-2010, 12:08 AM

I believe you have to signify that a char has been selected. Strings are wrapped in double quotes " and char (or single characters) are wrapped in single quotes '. So you would need something along the lines of.

Lets say the user presses c.

Code:

char shape=1;
scanf("%c",&shape);

Then shape='c'.

boilers969 · 10-11-2010, 12:13 AM

So I'm confused as to what I switch.
Would this work?

Code:

switch(char 's','h','f')
{
case s;
   break;
case h;
   break;
case f;
   break;
}

sag47 · 10-11-2010, 12:17 AM

Here, now that you're getting to know C some more check out paulsm's example again.

His switch statement is formatted how I described.

boilers969 · 10-11-2010, 12:20 AM

Do I need to put the switch into the while loop? I think I'll try that.

sag47 · 10-11-2010, 12:24 AM

The case is the same thing as the conditional if statement but more compact.

Code:

char shape=1;
shape='c';
if(shape=='a')
{
    return 0;
}
else if(shape=='b')
{
    return 0;
}
else
{
    return 1;
}

There the if statements are comparing the value stored in the shape variable to different conditions. Like if the contents of shape is equal the the character b then do something. Here is the exact same statement in a case...

Code:

char shape=1;
shape='c';
switch(shape)
{
    case 'a':
        return 0;
    case 'b':
        return 0;
    default:
        return 1;
}

It does the same thing as the if statements. Does this explain the how the case works a little?