I recently heard this was used as an interview question. I suspect there is a very simple answer; I must be over-thinking it.
Can you write Hello World in C without using any semi-colons? If so, how?
views:
2585answers:
8
+87
A:
#include<stdio.h>
main()
{
if(printf("Hello World \n"))
{
}
}
Robert Harvey
2010-05-02 18:39:00
So I built this as a win32 console application in VS2005; if it's foo.cpp, then I get a warning about implicit int. If I rename to foo.c, it works just fine, but I too wonder if this is only because I'm using the C++ compiler?
jeffamaphone
2010-05-02 18:43:25
@jeffamaphone: C99 would require 'int main()'; C++ already does. C89 did not require that, and MSVC really only supports C89.
Jonathan Leffler
2010-05-02 18:48:07
@Jonathan: Good to know.
jeffamaphone
2010-05-02 18:54:37
ha, I wouldn't have thought of it, despite the fact I write functions inside of conditional statements routinely. well done
Tom Dignan
2010-05-03 05:44:12
+66
A:
Any ANSI C solution with printf would require #include <stdio.h> or an explicit "manual" declaration of printf to be correct (the latter would need a semicolon though), since without the declaration of printf the behavior of the program is undefined.
One can also argue that by doing #include <stdio.h> you are implicitly introducing semicolons into your code :)
If you care to make it more compact, and also discourage any potential #include <stdio.h> protesters, use puts instead of printf
main() {
if (puts("Hello World")) {}
}
Of course, this is only valid in C89/90.
AndreyT
2010-05-02 20:13:50
+1, but to pick a nit `puts` will append a newline on its own, no need to include another in the literal.
jtb
2010-06-09 06:01:16
+3
A:
int
main (void)
{
while (puts ("Hello World!") && 0)
{}
}
Unfortunately, that omits the return statement. Some compilers will issue a warning, but it will still compile. The only one that REALLY works and is completely valid at the time of this writing (despite not producing a binary and lacking a main function in some form) is the one using #error "Hello World". Of course, that's if you're shooting for full C89/C90 compatibility with C99 as well. :P
Dustin
2010-05-02 21:11:41
susmits
2010-05-03 10:39:23
@susmits: The return value of `puts` is non-zero, so the loop would go on forever otherwise.
GMan
2010-05-03 18:54:47
And theoretically `puts` is better than `printf` in the regard that `printf` needs to scan for formatting instructions in the string before actually outputting any information whereas `puts` simply prints the string to `stdout`.
Dustin
2010-05-03 20:14:55
+21
A:
And here's a semicolonless quine, inspired by this question:
#include <stdio.h>
main(char* a){if(a="#include <stdio.h>%cmain(char* a){if(a=%c%s%c){if(printf(a,10,34,a,34)){}}}"){if(printf(a,10,34,a,34)){}}}
Compile with gcc.
KirarinSnow
2010-05-02 21:57:30
+9
A:
To be compliant, it should return a status code of 0 to the OS.
I like this version:
#include<stdio.h>
#include<stdlib.h>
int main(void)
{
if (printf("Hello World\n"), exit(0), 0) { }
}
(answer edited based on comments. Tested under VS 2010 as Win32 Console App)
abelenky
2010-05-02 22:04:53
What compiler is that? I've tried it on several myself, and it worked fine.
abelenky
2010-05-03 04:58:41
A C99 program returns 0 to the OS automatically. A C89/90 returns undefined value, but it doesn't make the program non-compliant.
AndreyT
2010-05-03 13:54:08
@abelenky: Your code is not valid because `exit` is a `void` function. The only reason it might compile (as it apparently did in your case) is that you failed to include the declaration of `exit` (it is in `stdlib.h`) and the compiler assumed that it returns `int`. Needless to say, in such case the behavior of your program is undefined, even if it compiles. In order to make it valid you need to do `if (printf(...), exit(0), 0)` for example, as GMan did in his deleted answer. But what you have now is plainly invalid.
AndreyT
2010-05-03 15:55:05
Indeed, this is what I have as my deleted answer. I deleted it because there is no need to try to return anything in C99. And if you are using C89/90, we might as well go with @AndreyT's answer, which I personally find to be the best answer.
GMan
2010-05-03 18:53:09
+5
A:
file name:
void main(){if(puts("Hello, World!")){}}
file contents:
A
compile with:
-istdio.h -DA=__FILE__
Time Machine
2010-05-03 02:39:22
@jeffamaphone there's always Mac OS X, which even allows `/`es in filenames.
Time Machine
2010-05-04 14:04:43
A:
Can you write Hello World in C without using any semi-colons? If so, how?
Sought out answer already provided, but given the question...
[sarcasm]
int main()
{
// Hello World
}
[/sarcasm]
I think a lot of interview questions are often very poorly worded. I was once asked, "How many bits are required to represent the number, 32?" I had to ask, "for what range, and is this for integers only?" The interviewer answered that it was for integers and starting from zero, so I said 6. Then he said that was wrong and the correct answer was 5. I told him he was wrong as that would assume the range [1, 32], not [0, 32] which would have 33 unique values and would require 6 bits. I got the job but the interview was silly. Sometimes it seems like they just came up with the question on the spot.