If you put ac into a capacitor, and the discharge of the capacitor is the output.
Then the ac will charge it from neutral to positive, then youll get a back charge from the ac, and this will make it go back to neutral again. (so then you dont get a negative half cycle!)
The problem is, if the capacitor is discharging, then this isnt true anymore, but you have to put a resistor on it anyway, to make the ac not take the discharge path and then this will start to make the capacitor act as a rectifier again.
So a capacitor discharging into a resistor, might be able to rectify current too, without a diode.
Then the ac will charge it from neutral to positive, then youll get a back charge from the ac, and this will make it go back to neutral again. (so then you dont get a negative half cycle!)
The problem is, if the capacitor is discharging, then this isnt true anymore, but you have to put a resistor on it anyway, to make the ac not take the discharge path and then this will start to make the capacitor act as a rectifier again.
So a capacitor discharging into a resistor, might be able to rectify current too, without a diode.