Simple Thermostat rule (sensor in ,valve control)

Setup, Configuration and Use Scripts & Rules
4

Ok I solved the problem, but I still do not understand why the following code work while the previous one does not

rule "heating water thermostat"
    when
		Item B_Temperature_Water_Setpoint changed or
		Item B_Temperature_tgS_heating_water changed 
	then
	
	var Number cur_temp = B_Temperature_tgS_heating_water.state 
	var Number setpoint = B_Temperature_Water_Setpoint.state 
        val  hysteresis = 0.5
	
	if ((cur_temp).floatValue < ((setpoint).floatValue - hysteresis)) {
			if (boiler_outb0.state == OFF) {
				sendCommand(boiler_outb1, OFF)
				sendCommand(boiler_outb0, ON)
				}
			}
		else {
			sendCommand(boiler_outb0, OFF)
			}
end