Possible Duplicates:
How to convert a single char into an int
Character to integer in C
Can any body tell me how to convert a char to int?
char c[]={'1',':','3'};
int i=int(c[0]);
printf("%d",i);
When I try this it gives 49.
views:
9868answers:
3atoi takes a char* not a char.
Mehrdad Afshari
2009-05-15 12:51:29
Isn't that just semantics? A char* gives a char as well, just pass the address. But ok, I didn't look at the specifics, my C is starting to get kind of rusty.
Frans Bouma
2009-05-15 12:53:10
Paul Tomblin
2009-05-15 12:54:02
Nope, to be correct, it expects a NULL-terminated char* not just an address.
Mehrdad Afshari
2009-05-15 12:54:06
@Frans,Noldorin: I would consider it very dangerous to "just" pass a pointer to a char array which isn't NULL terminated to a function expecting a NULL terminated string. In the example, remove the colon from the char array and the code will read uninitialized memory.
Tobi
2009-05-15 12:59:35
+4
A:
int result = charValue - '0';
so your code would be:
printf("%d", i - '0');
Mehrdad Afshari
2009-05-15 12:51:08
+13
A:
In the old days, when we could assume that most computers used ASCII, we would just do
int i = c[0] - '0';
But in these days of Unicode, it's not a good idea. It was never a good idea if your code had to run on a non-ASCII computer.
Edit: Although it looks hackish, evidently it is guaranteed by the standard to work. Thanks @Earwicker.
Paul Tomblin
2009-05-15 12:52:15
Not working .I expect answer as 1 but it gives a 6 digit nummber garbage i think
Cute
2009-05-15 13:05:26
Sorry, I changed it to c[0] since that's what the example code uses.
Paul Tomblin
2009-05-15 13:12:06
How could unicode affect the representation of a digit in a char variable?
David Sykes
2009-05-15 14:49:23
@David, you're probably right. I was just thinking that there might be things in the Unicode character set that look like digits but aren't. But really, the problem is other character sets, since the standard does not guarantee that 0-9 are contiguous integer values.
Paul Tomblin
2009-05-15 15:18:58
@Paul, actually the C standard does guarantee that. Paragraph 2.2.1 "In both the source and execution basic character sets, the value of each character after 0 in the above list of decimal digits shall be one greater than the value of the previous." So your answer is perfectly valid in a conforming C implementation.
Daniel Earwicker
2009-05-27 08:43:16