Thread: Very strange problem!

This reads a string and prints each character in a new line.

Code:

float rt, gt;
int a;
      
printf ("Input value rt:\n");
scanf ("%f", &rt);
printf ("Input value gt:\n");
scanf ("%f",&gt);

int i;
char str1[50];
printf ("Input string\n");
gets(str1);
i = 0;
while (str1[i]!= '\0')
    {
          if (str1[i] == ' '){ i++;  continue;}
          
          if (str1[i]!= '+' || str1[i]!= '-' || str1[i]!= '*' || str1[i]!= '/')
          {
               printf("\n%c", str1[i]);
           }
          else 
          {
               printf("\n%c", str1[i]);
          } 
     
     i++;       
    }


scanf("%d", &a);

But like it is written above it doesn't work. I don't have a clue of what the problem is but the thing is that, without this part...

Code:

printf ("Input value rt:\n");
scanf ("%f", &rt);
printf ("Input value gt:\n");
scanf ("%f",&gt);

...it runs great. Add this and it stops working.

Any help, please?

1. You shouldn't be using gets at all.
2. Even once you change gets to fgets, scanf and fgets don't play nice together. If you insist on mixing them, you will have to take care of the newline character that scanf leaves behind yourself. (There's an FAQ on this.)

Originally Posted by NeonBlack

You should describe how it "stops working"
Does it give the wrong result? Does it crash?

Also you really ought to consider rewriting your loop.

It doesn't print the string. After I input the string and press enter the program abruptly ends. If scanf isn't present in the code, it works great and prints the string.

1. You shouldn't be using gets at all.
2. Even once you change gets to fgets, scanf and fgets don't play nice together. If you insist on mixing them, you will have to take care of the newline character that scanf leaves behind yourself. (There's an FAQ on this.)

I have used fgets and it does exactly the same thing. What should I use to make it work?

You could try to use the idea about using fgets right here

Originally Posted by nonoob

This part does not make sense:

Code:

if (str1[i]!= '+' || str1[i]!= '-' || str1[i]!= '*' || str1[i]!= '/')

The corollary is

Code:

if ( ! (str1[i] == '+' && str1[i] == '-' && str1[i] == '*' && str1[i] == '/'))

... which is clearly impossible to be met.

In fact, that part of the code works fine, although I'm going to rewrite it later. The thing between the scanf and fgets or gets is the problem.

Originally Posted by $l4xklynx

You could try to use the idea about using fgets right here

Tried it that way, unfortunately it doesn't work. Does the same thing, doesn't print the string.

Or you could just use isalpha() to capture all alpha characters from the input and disregard those non-alpha characters.

Originally Posted by no_one_knows

Tried it that way, unfortunately it doesn't work. Does the same thing, doesn't print the string.

Were you able to enter a string using gets()? if not, then the string will not be printed. Prior to input string using gets you have 2 scanf()'s, I presume, that you won't be able to input any value to gets() because of the excess buffer from scanf(). So it would be good to use fgets for all user inputs and convert those chars to float using atof().

Originally Posted by no_one_knows

In fact, that part of the code works fine, although I'm going to rewrite it later. The thing between the scanf and fgets or gets is the problem.

No it doesn't. Likely it's not what's causing your immediate problem but I'm sure it will not give you the correct result when you resolved your first problem.

Originally Posted by tabstop

2. Even once you change gets to fgets, scanf and fgets don't play nice together. If you insist on mixing them, you will have to take care of the newline character that scanf leaves behind yourself. (There's an FAQ on this.)

I will repeat tabstop's comment here, as it provides you the references to understanding your problem.

Are you using a microsoft compiler?

If so, check PRB: "Floating-point Support Not Loaded" Error with scanf()
Try initializing rt and gt before calling scanf.
Its crazy, I know.

And, unfortunately, it still doesn't work.

I know that it will not work according to the code that you posted.

I don't see the relation of the 2 scanf() input to the goal of your program which is to print chars to a new line by line. Anyway the colored red statement in the code is causing an excess buffer.

Code:

float rt, gt;
int a;
      
printf ("Input value rt:\n");
scanf ("%f", &rt);  //You can input but with excess
printf ("Input value gt:\n");
scanf ("%f",&gt);  //You can input but with excess


int i;
char str1[50];
printf ("Input string\n");
fgets(str1, 50, stdin); //Excess go here, you cannot input

If you cannot input any value for fgets() then there will be no printed string. Use fgets for each input to avoid excess buffer.