Thread: populating arrays

Here's an example:

Code:

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>

/* compile -std=c99 */

float getInput() {
	char input[32], *tptr;
	float val;
	printf("Enter any kind of number: ");
	fgets(input,32,stdin);
	errno = 0;
	val = strtof(input,&tptr);
	if ((errno) || ((val == 0) && (tptr == input))) {
		puts("That input is not valid!  Try again...");
		val = getInput();
	} 
	return val;
}

int main() {
	float array[6];
	int i;
	for (i=0; i<6; i++) array[i] = getInput();
	for (i=0; i<6; i++) printf("%f\n",array[i]);
	return 0;
}

This may seem a bit complex, but the form should be easy to follow. The verification is slightly lame since strtof will go to some length to take a number, eg, "1324mdsf" will be 1324 and "3,5" will be 3, but this at least means you will end up with a valid number submitted to the array. And you get an example of how to error check the strtof/l/d() functions, which are useful in verifying input this way.

NB. strtof is a c99 function and needs to be compiled with that in mind!

thanks Adak i think i got what you said there

roaan thanks for the link i will read it

MK27 thanks for the example but theres some stuff in there i haven't learn yet floats and strtof yet so i didnt understand it fully


i want to have so that if the user enters a number but if the number doesnt meet the requirements it doesnt store it in the array

i wrote some code quickly just now
i am not sure if i am doing it right

is is possible to do to this in one function

Code:

int getInput(int x);  
int okInput(int y);
  main()   

{
int variable, maxarr, usri;
maxarr = 10
for (i=0; i < maxarr; i++);
variable = getInput(usri);
if (okInput (variable))
        array[i] = variable

}           
int getInput(int x);
{
 printf("Enter a number");
scanf("%d, &usri");
return x;
}
int okInput(int y);
{
if (y <0)
    break;
else
return y;
}

Originally Posted by jafa401

is is possible to do to this in one function

Yeah, and using scanf() is fine too. But you need to use the return value of scanf to determine whether or not it retrieved a number. Then you can check that, and do what I did to repeat if scanf() failed -- here's a pseudo code version:

Code:

int getInput () {
     int value;
     ask for input
     r=scanf("%d%*c",&value);
     if (r != 1) {
          puts error message;
          value = getInput();
     }
     return value;
}

About the bit in red: %*c will trap the "trailing newline" which will get left in the input buffer and cause a problem (do it first without %*c and you will understand what the problem is).

I think that okInput would be more readable as:

Code:

int okInput(int y)
{
    return y >= 0;
}

after all, the extra variables are not necessary, and now it is easy to see that "ok input" means that "the input is greater than or equal to 0".

Originally Posted by jafa401

i want it so if the user enters umm a negative number it will not store it in the array it just continues on with out error msg.

Do you want to use an error msg at all? Anyway, if not, you could just take that part out, and simplify by setting "value" to -1 initially. Then, if scanf() doesn't get a proper number, value will still be -1 and you can use that as the if condition -- so no more need to check scanf's return value"

Code:

int value = -1;
scanf("%d%*c",&value);
if (value < 0) value = getInput();
return value;

Originally Posted by nonoob

Wow, lots of people doing people's homework today!

It is reasonable to suggest improvements in code after the person has actually posted a reasonable attempt.