Dear c/g++ programmer (on ubuntu linux 11.04):
I copied and test a simple random number generate program
-----------------
#include <algorithm>

#include <vector>

#include <iterator>

#include <iostream>

#include <cstdlib>



using namespace std;



struct RndIntGen

{

RndIntGen(int l, int h)

: low(l), high(h)

{ }

int operator( )( ) const {

return low + (rand( ) % ((high - low) + 1));

}

private:

int low;

int high;

};



int main( ) {

srand(static_cast<unsigned int>(clock( )));

vector<int> v(5);

generate(v.begin( ), v.end( ), RndIntGen(1, 6));

copy(v.begin( ), v.end( ), ostream_iterator<int>(cout, "\n"));

}
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it can compile and run, and for most of people will think it run well, but for me
why it always produce same result, if it is really random and based on clock?
eric@eric-Inspiron-8600:~/cppcookbook/download$ ./a.out
2
5
4
2
6
----------------------------------------------------------
this is from Example 11-13 of book(C++ cookbook), you always can download from
http://examples.oreilly.com/9780596007614/
to test by yourself

Highly appreciate your explanation and thanks a lot in advance, Eric

it's probably because it should really be time(), not clock(). clock() returns the CPU time used, which depending on the clock frequency, will always be the same right at the beginning when in gets called.

I follow your suggestion to modify it to time()
then I get compile error(on my g++4.5.2)
------------
eric@eric-laptop:~/cppcookbook/ch11$ g++ Example11-11.cpp
Example11-11.cpp: In function ‘int main()’:
Example11-11.cpp:14:41: error: too few arguments to function ‘time_t time(time_t*)’
/usr/include/time.h:186:15: note: declared here
----------------------
so can you be specific write out workable code?
srand(static_cast<unsigned int>(time())); // not this, but based on this
thanks a lot in advance, Eric