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// FILE: throttle.h
// CLASS PROVIDED: throttle (part of the namespace main_savitch_chapter2)
//
// CONSTRUCTORS for the throttle class:
// throttle( )
// Postcondition: The throttle has one position above the shut_off position,
// and it is currently shut off.
//
// throttle(int size)
// Precondition: size > 0.
// Postcondition: The throttle has size positions above the shut_off
// position, and it is currently shut off.
//
// MODIFICATION MEMBER FUNCTIONS for the throttle class:
// void shut_off( )
// Postcondition: The throttle has been turned off.
//
// void shift(int amount)
// Postcondition: The throttle's position has been moved by
// amount (but not below 0 or above the top position).
//
// CONSTANT MEMBER FUNCTIONS for the throttle class:
// double flow( ) const
// Postcondition: The value returned is the current flow as a
// proportion of the maximum flow.
//
// bool is_on( ) const
// Postcondition: If the throttle's flow is above 0 then
// the function returns true; otherwise it returns false.
//
// VALUE SEMANTICS for the throttle class: (See discussion on page 51.)
// Assignments and the copy constructor may be used with throttle objects.
#ifndef MAIN_SAVITCH_THROTTLE
#define MAIN_SAVITCH_THROTTLE
namespace main_savitch_2A
{
class throttle
{
public:
// CONSTRUCTORS
throttle( );
throttle(int size);
// MODIFICATION MEMBER FUNCTIONS
void shut_off( ) { position = 0; }
void shift(int amount);
// CONSTANT MEMBER FUNCTIONS
double flow( ) const { return position / double(top_position); }
bool is_on( ) const { return (position > 0); }
private:
int top_position;
int position;
};
}
#endif
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