Arduino rosserial problem compilation

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Hello , i'm trying to compile the examples for Arduino, for example the Hello_World (or whatever) and i got this error:

HelloWorld.pde:-1: error: ‘ros’ has not been declared
HelloWorld.pde:-1: error: expected constructor, destructor, or type conversion before ‘nh’
HelloWorld.pde:-1: error: ‘std_msgs’ has not been declared
HelloWorld.pde:-1: error: expected constructor, destructor, or type conversion before ‘str_msg’
HelloWorld.pde:-1: error: ‘ros’ has not been declared
HelloWorld.pde:-1: error: expected constructor, destructor, or type conversion before ‘chatter’
HelloWorld.cpp: In function ‘void setup()’:
HelloWorld.pde:-1: error: ‘nh’ was not declared in this scope
HelloWorld.pde:-1: error: ‘chatter’ was not declared in this scope
HelloWorld.cpp: In function ‘void loop()’:
HelloWorld.pde:-1: error: ‘str_msg’ was not declared in this scope
HelloWorld.pde:-1: error: ‘chatter’ was not declared in this scope
HelloWorld.pde:-1: error: ‘nh’ was not declared in this scope

i'm working on ROS Electric, I really Need Help!