Permutations of chars in string

[serge]

Hello

I found this code on the internet

#include <iostream>
#include <string>

using namespace std;

int main()
{
	std::string default = "12345";

	int perm=1, digits=default.size();
	for (int i=1;i<=digits;perm*=i++);
	for (int a=0;a<perm;a++)
	{
		std::string avail=default;
		for (int b=digits,div=perm;b>0; b--)
		{
			div/=b;
			int index = (a/div)%b;
			printf("%c", avail[index] );
			//avail[index]=avail[b-1]; // fast but not lexigraphic order
			avail.erase(index,1) ; // lexigraphic correct order
		}
		printf("\n");
	}
	printf("permutations:%d\n",perm);
	return 0;
}

But I am getting an error:

perm.cpp: In function ‘int main()’:
perm.cpp:8: error: expected unqualified-id before ‘default’
perm.cpp:10: error: expected primary-expression before ‘default’
perm.cpp:10: error: expected ‘,’ or ‘;’ before ‘default’
perm.cpp:14: error: expected primary-expression before ‘default’
perm.cpp:14: error: expected ‘,’ or ‘;’ before ‘default’
make[1]: *** [perm] Error 1
make: *** [run] Error 2

What is missing? Thanks a lot

Serge

[manasij7479]

This is exactly why you should try to write code instead of ^C + ^V.
'default' is a reserved word.
&& Try not to mix C and C++ io.
(btw...where is stdio.h ?)

[M1cKeY]

Obviously this is C++ code..
Try to use C++ compiler. I copied ur code to my new project, it passed.

[laserlight]

Obviously this is C++ code..
Try to use C++ compiler. I copied ur code to my new project, it passed.

Here are the error messages from the Comeau online C++ compiler:

MODE:strict errors C++ C++0x_extensions

"ComeauTest.c", line 8: error: expected an identifier
  	std::string default = "12345";
  	            ^

"ComeauTest.c", line 10: error: expected an expression
  	int perm=1, digits=default.size();
  	                   ^

"ComeauTest.c", line 14: error: expected an expression
  		std::string avail=default;
  		                  ^

3 errors detected in the compilation of "ComeauTest.c".

Here are the error messages from g++ 4.4.5:

test.cpp: In function ‘int main()’:
test.cpp:8: error: expected unqualified-id before ‘default’
test.cpp:10: error: expected primary-expression before ‘default’
test.cpp:10: error: expected ‘,’ or ‘;’ before ‘default’
test.cpp:14: error: expected primary-expression before ‘default’
test.cpp:14: error: expected ‘,’ or ‘;’ before ‘default’
test.cpp:19: error: ‘printf’ was not declared in this scope
test.cpp:23: error: ‘printf’ was not declared in this scope
test.cpp:25: error: ‘printf’ was not declared in this scope

So yes, it is intended to be C++ code, but it isn't valid C++. Your compiler might allow the printf despite the missing #include <cstdio> because <cstdio> could have been included via <iostream>, but that does not mean that failing to #include <cstdio> is okay, as the error messages for g++ show. The use of default as a variable name is clearly an error, and allowing it could well be considered a bug with your compiler (or a non-standard "feature").