In file included from /usr/include/c++/4.4/unordered_map:35, from replace.cpp:4: /usr/include/c++/4.4/c++0x_warning.h:31:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options. replace.cpp:8: error: expected constructor, destructor, or type conversion before '<' token replace.cpp:9: error: expected constructor, destructor, or type conversion before '<' token replace.cpp: In function 'int main()': replace.cpp:37: error: 'M' was not declared in this scope replace.cpp:43: error: 'it' was not declared in this scope replace.cpp:43: error: 'M' was not declared in this scope replace.cpp:47: error: 'UINT_MAX' was not declared in this scope replace.cpp:15: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result replace.cpp:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result