Latch

Description: Latch On or Off. This function allows a transient change of a variable to be captured. Its return value is determined by the rules listed in the comments section.

Returns: Boolean

Usage: Steady State.

Format: Latch(Set, Reset)

Parameters: Set { Boolean } { required } { no default }

Any numeric expression. If true (i.e. not equal to 0), the latch is set.

Reset { Boolean } { required } { no default }

Any numeric expression. If true (i.e. not equal to 0), the latch is reset.

Comments: This function starts in a state with its return value being a valid 0 (false). The change in values is governed by the following rules :

Set	Reset	Old Value	New Value
False	False	False	False
False	False	True	True
Either	True	Either	False
True	False	Either	True
Invalid	True	Either	False
Either	Invalid	Either	Invalid

If both the Set and Reset are false, the latch value remains unchanged. Note that a true Reset overrides a true Set.

This function resets its parameters after they evaluate to true. This is significant only for functions which can be reset, such as MatchKeys, TimeOut, Intgr and RTimeOut.

Example:

motorOn = Latch(MatchKeys(1,"1") { Set the var with a "1" },

MatchKeys(1,"0") { Reset the var with a "0" });

This controls the variable motorOn from the keyboard. MotorOn initially starts as 0. When 1 is pressed on the keyboard, the latch is set and motorOn becomes 1. When 0 is pressed on the keyboard, the latch is reset and motorOn becomes 0.