logpl incorrectly plots paired commands in one case

[wehimwich]

This is complicated to explain.

logpl can plot data from paired commands. The first command of a pair (its description in logpl.ctl starts with a $) is associated with the second of the pair (its description ends with $). logpl selects the data to plot based on the first command. The next following instance of the second command has the value to be plotted. This can be be useful for commands that identify what is being sampled (e.g. a channel defined by pcalports=) in one command and the sampled data appears in a following command (e.g., amplitude and phase from decode4/pcal usb).

The problem arises if the corresponding second command is missing (perhaps due to a time-out) before the next instance of the first command. logpl thinks the next occurring second command should be used, even if the intervening first command identifies different data. The result is that data from two different selections will appear on one plot. That makes a mess.

More succinctly: There is a match on the second command of a pair if the first command of that pair with a different string has occurred since the first command with the right string. This can occur if the expected second command is not present between the first command with the right string and one with the wrong string. The second command after the first command with the different string matches instead.