M
mikhal80
Is it possible to write a program which would print out it's own
source code, using C++?
source code, using C++?
A program which would print out it's own source code - possible ornot?
J
Jensen Somers
Yes.
- Jensen
T
tragomaskhalos
Google "quine".
A
anon
yes, here is one example for free:
K
Kira Yamato
deep, philosophically... lol.
V
Victor Bazarov
Kira said:
It probably is. But my dumb compiler complains that there is no
'main' in my program...
V
P
Pascal Bourguignon
Yes, that's trivial.
--
__Pascal Bourguignon__ http://www.informatimago.com/
Until real software engineering is developed, the next best practice
is to develop with a dynamic system that has extreme late binding in
all aspects. The first system to really do this in an important way
is Lisp. -- Alan Kay
P
Pascal Bourguignon
Victor Bazarov said:
Ok, so you need at least a main.
int main(){
// add something here...
return 0;
}
--
__Pascal Bourguignon__ http://www.informatimago.com/
Until real software engineering is developed, the next best practice
is to develop with a dynamic system that has extreme late binding in
all aspects. The first system to really do this in an important way
is Lisp. -- Alan Kay
V
Victor Bazarov
Pascal said:
Weird. This one doesn't print its own source code. Why?
V
B
Bo Persson
Victor said:
But other compilers actually once compiled this, ran it, and produced
an identical empty output.
This entry in the 1994 Obfuscated C contest won its class
http://www.ioccc.org/1994/smr.c
http://www.ioccc.org/1994/smr.hint
and changed the category into "Smallest, non-empty, self-replicating
program".
Bo Persson
V
Victor Bazarov
Bo said:
Can you please state which compilers did (or do)?
V
K
kwikius
Heres my effort FWIW. (BTW, if its a homework assigmment then I
wouldnt recommend handing the following in).
Also though it compiles in gcc 3.4 I don't know that the fstream
declaration in the for loop is actually legal. I have a funny idea it
isnt for some reason...
#include <fstream>
#include <string>
#include <cassert>
#include <iostream>
template <typename T1, typename T2>
inline
void apply(T1* f,T2 & out)
{
std::string str;
for(
std::ifstream in(f);
getline(in,str);
out << str <<'\n'
){}
}
int main()
{
apply(__FILE__,std::cout);
}
regards
Andy Little
R
red floyd
Victor said:
Allow me to correct Pascal's code:
int main()
{
// add something here to print its own source.
// this is left as an exercise to the reader
return 0;
}
A
anon
Victor said:
You need to tweak it a bit (different compiler options). My linker
complains:
(.text+0x18): undefined reference to `main'
J
James Kanze
For what system? In a hosted environment, a C++ program must
contain a function main somewhere.
J
James Kanze
Why shouldn't it be?
When I tried it, it worked in the directory where I compiled it,
but when I copied it to ~/bin, and invoked it from there, it
output an earlier suggestion---the one without a main.
K
kwikius
I think I had problems once upon a time. It may have been ambiguity
with function declarations, not being in a for statement, which was
the problem before though.
Yes! It was hard solving that one as well but I figured it eventually.
Isnt that even more useful than the original application?... its
multipurpose
IIRC the file macro gives the full path with VC++ but not gcc.
regards
Andy Little
P
Pascal J. Bourguignon
kwikius said:Yes! It was hard solving that one as well but I figured it eventually.
Isnt that even more useful than the original application?... its
multipurpose
But it's not what's specified.
So how could you write a program that writes a copy of its source,
without relying on run-time external files other than the executable,
since they may not be available?
P
Puppet_Sock
That's old. The trick is to get the compiler
to spit out the entire source code from
messages produced during compilation.
Socks
A
Alf P. Steinbach
* Pascal J. Bourguignon:
quine.
Cheers, & hth.,
- Alf
quine.
Cheers, & hth.,
- Alf