Thread: Array/Function Troubles

Hello, i recently saw the film The Prestige, and one of the actors keeps a diary, and writes in it using a keyword cipher. I decided to make a program that when i input text it outputs the text in the cipher (switches one letter for another letter).

I think i have written my function declaration wrong, and when im calling the function i think i've done it wrong, and when i prototype it i think i've done it wrong.

Also, how do i assign 'x' to the number that the array is on?
'x' needs to be initialised, but i am not sure how i initialize it to this position?

Take a look at the code to understand what i mean.

Thanks in advance to anyone who can help me out

Code:

#include <stdio.h>

void fConvert(int, char[]);

int main(void)
{
	char cText[100];
	int x;

	printf("Enter text:");
	fgets(cText, 100, stdin);

	if(cText[x] != '\0')
	{
		fConvert(x, cText);
	}

	return 0;
}

void fConvert(int a, char b[100])
{
	for(a; b[a]!='\0'; a++)
	{
		switch(b[a])
		{
			case 'a':
				printf("t");
				break;
			case 'b':
				printf("e");
				break;
			case 'c':
				printf("s");
				break;
			case 'd':
				printf("l");
				break;
			case 'e':
				printf("a");
				break;
			case 'f':
				printf("b");
				break;
			case 'g':
				printf("c");
				break;
			case 'h':
				printf("d");
				break;
			case 'i':
				printf("f");
				break;
			case 'j':
				printf("g");
				break;
			case 'k':
				printf("h");
				break;
			case 'l':
				printf("i");
				break;
			case 'm':
				printf("j");
				break;
			case 'n':
				printf("k");
				break;
			case 'o':
				printf("m");
				break;
			case 'p':
				printf("n");
				break;
			case 'q':
				printf("o");
				break;
			case 'r':
				printf("p");
				break;
			case 's':
				printf("q");
				break;
			case 't':
				printf("r");
				break;
			case 'u':
				printf("u");
				break;
			case 'v':
				printf("v");
				break;
			case 'w':
				printf("w");
				break;
			case 'x':
				printf("x");
				break;
			case 'y':
				printf("y");
				break;
			case 'z':
				printf("z");
				break;
			default:
				printf("Error, was not a letter");
				break;
		}
	}
}

> if(cText[x] != '\0')
What's the value of x here?

Did you perhaps mean to use a for loop to step through the string?

Also, if you're trying to pass the whole array, then the prototype should be
void fConvert(int, char[ ]);

And the call should be
fConvert(x, cText);

Since it seems that x (or a in the funtion) is never used, you may as well remove it as a parameter, and just make it local within the function.

Here's a for loop.

Code:

void fConvert(int a, char b[100])
{
	for(a = 0; a < '\0'; a++)

However, the condition will ensure that you're never enter the loop. Remember, you're checking for the null termination of the array, not something on the index.

Code:

for(a = 0; b[a] != '\0'; a++)

Further, why pass in a at all if you're just going to be setting it to zero first thing?

Originally Posted by AstraI

still can't see what i'm doing wrong

hello.c(12): error 534: (Warning -- Ignoring return value of function 'fgets(char *, int, struct _iobuf *)'

if(cText[x] != '\0')
hello.c(14): error 530: (Warning -- Symbol 'x' (line 9) not initialized)

for(a = 0; a < '\0'; a++)
hello.c(24): error 681: (Warning -- Loop is not entered)

hello.c(111): error 952: (Note -- Parameter 'b' (line 22) could be declared const)
hello.c(111): error 818: (Info -- Pointer parameter 'b' (line 22) could be declared as pointing to const)

hello.c(112): error 766: (Info -- Header file 'stdlib.h' not used in module 'hello.c')

For the start the above warning should be fixed...

@vart, ty for the help.

I thought fgets was a function in stdlib.h which is why i included that at the top. Is it in stdio.h?

@ssharish2005, if i put ''cText[0]'' it would only mean the first thing inputted being end of array, but i want it to be for the entire array, can i still do that this way?

@anybody - if i take out all the x's, in this part i'll be left with:

Code:

	if(cText[] != '\0')
	{
		fConvert(cText);
	}

But, i want: cText[HERE TO SHOW WHAT POSITION ITS AT]

EDIT: updated code in first post

Originally Posted by Astra

@vart, ty for the help.

Use English, please

Originally Posted by Astra

I thought fgets was a function in stdlib.h which is why i included that at the top. Is it in stdio.h?

You can comment some h-file and see - what warnings appear.
Or you can use something like msdn.

Would that not set i to 0 each time it goes round? I still don't know why i don't need x. Should i use the for loop that ssharish has written, and also the loop in my fConvert?

ty vart.

No you definitely need only one loop for your solution

For loop inside function use

Code:

void fConvert(char[]);

for declaration and

Code:

fConvert(cText);

for the call

OR
in the solution of ssharish2005
the declaration will be

Code:

void convert(char);

and this function will convert and print only 1 charachter

Originally Posted by Astra

i initialised x to 0 at the top and now it works. :/

1. You can just remove the x and use directly

Code:

if(cText[0] != '\0')

to check if the string is empty
2. You can remove this check also because the

Code:

 for(a=0; b[a]!='\0'; a++)

makes the same check inside the function
3. You can remove the x from fConvert parameters - becouse you don't need its value and as said before - use local variable

All this does not checnge the logic of the program. Just makes it easier to read and "clearer"