#10 simple example fails to compile without #include <iostream>

[Christopher Harvey]

gcc --version
gcc (GCC) 4.1.2 (Gentoo 4.1.2 p1.1)
Copyright (C) 2006 Free Software Foundation, Inc.

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#include <tvmet/tvmet.h>
int main(int argc, char **argv) {}

g++ main.cc
/usr/include/tvmet/TvmetBase.h: In member function 'std::ostream& tvmet::IndentLevel::print_xpr(std::ostream&) const':
/usr/include/tvmet/TvmetBase.h:63: error: no match for 'operator<<' in 'os << " "'
make: *** [all] Error 1

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#include <iostream>
#include <tvmet/tvmet.h>
int main(int argc, char **argv) {}

//works fine.