How to distinguish between characters and numers. 1

[Taxidriver]

Hello guys,
can somebody tell me how to write a code that accepts numbers in input but stops reading when you type a character?

 

[rwb1959]

This depends on the size/type of number you are taking as input
but for instance, taking integers as input you can do...

while((c = getchar()) != EOF)
{
if((c & 0x00ff) == 'q')
exit(0)
else
...do somthing
}

Since "c" is a signed int (to check for EOF), I mask the upper bits to 0.

 

[Jay1Roy]

Hey,

You can also give change to scanf statement for this assignement, try this...

        char char_ar[20];
        scanf("%[0-9]",char_ar);

when you run this snippet and enter 1234ROY, char_ar will only store 1234, rejecting all characters after that.

Howzz that?

Roy.

 

[Taxidriver]

The problem is that my program should read numbers(integers) in order to calculate the average of these numbers. It should stop reading when it's introduced a non numerical character.
Can you be more explicative? Thanks

 

[Jay1Roy]

Well, I suppose you can start with the snippet above... ok, take the following code for eg:

char tmp_str[10]=" ";
int ctr=-1, total=0;

do 
{
	total+=atoi(tmp_str); //Converts the string to int.
	printf("\n\tEnter the next number:");
	ctr++;
	fflush(stdin);
}
while(scanf("%[0-9]",tmp_str));
//scanf returns 0 if nothing is read eg. in case of non-num.

printf("\nNumbers Entered:%d average is: %f",
        ctr,
       ((float)total/(float)ctr));

Well, I think that's it? B-)

Roy.

 

[Taxidriver]

RoyOBoy thanks for your prompt reply and sorry if I didn't write back again to tell you about the code that you kindly wrote.
It was fine but for one thing. The program stops reading also if you write a negative number. How should I modify it to make him accepts negative numbers as well as positive numbers?
Thank you.

 

[bigtamscot]

The reason your program stops when entering a negative number is that you are entering the numbers into a char string. The program recognizes the minus sign as a ascii character.

way round it ?

char string[11], result[10], *ptr;
int count = 0;
printf("Enter a string up to 10 charcters :"
gets(string);
ptr = string;
while(*ptr)
{
if(!isdigit(*ptr))
{
if(*ptr != '-')
break;
}
else
result[count++]= *ptr;
}
result[count] ='\0';
printf("Numeric entries are %s", result);


Hoping to get certified..in C programming.

 

[bigtamscot]

CORRECTIONS TO MY CODE ABOVE

#include <stdio.h>
#include <ctype.h>

void main ()
{
char string[11], result[11], *ptr;
int count = 0;

printf(&quot;Enter a string up to 10 charcters :&quot;
gets(string);
ptr = string;
while(*ptr)
{
if(!isdigit(*ptr))
{
if(*ptr != '-')
break;
else
result[count]= *ptr;
}
else
{
result[count]= *ptr;
}
ptr++;
count++;
}
result[count] ='\0';
printf(&quot;Numeric entries are %s&quot;, result);
} Hoping to get certified..in C programming.

 

[Jay1Roy]

Hey guys,

bigtamscot, am afraid your point isn't correct. Well, what I am reading through scanf is a string so all it reads IS ascii.

Taxidriver, all you have to do is to play around with the format specifier string. just add a '-' in the wish list of characters you want it to read for you. See the code below:

scanf("%[

-

0-9]",tmp_str)

May be I'll give you some examples... if you wanted to accept only lower alpabets, your format string would be %[a-z].

Lower case alphabets and digits %[a-z0-9]

If the entry can be only vowels %[aeiou] thus only characters 'a','e','i','o','u' in any combination would be accepted.

Never imagined format strings could be this powerful? Tricky isn't it?

I hope the post was informative...;-)

Roy.

 

[Taxidriver]

Hey, no, I've never imagined that this format was so powerful.
Thanks Roy, the post was informative.