track()

track() sets a variable with a tracking value that matches another value. The name of the variable is either track or a non-reserved qualifier on the function.

For example:

$[*][ track.my_cities(#city, #zip) ]

This path creates a variable called my_cities. Within that variable each city name will track a zip code. This is a dictionary structure. If no name qualifier is present the variable name is 'track'.

Behind-the-sceens the tracking data structure is like:

my_cities["Washington"] == 20521

track() can take the onmatch qualifier. If onmatch is set and the row doesn't match, track() does not set the tracking variable

track() is a side-effect with no effect on a row matching.

track() can take a third argument, 'collect'. If 'collect' is passed the tracked values are pushed on a stack variable. No third argument results in the tracked value being replaced at every line.

Note that track() treats all values as strings; whereas, track_any() attempts to convert values. In the zip code example track_any() would not capture leading zeros, but track() would.

Data signatures
track( track under: $${\color{green}str}$$, tracking value: $${\color{green}Any}$$, ['collect': $${\color{green}Any}$$] )

Call signatures
track( track under: Term ǁ Variable ǁ Header ǁ Function ǁ Reference, tracking value: Term ǁ Variable ǁ Header ǁ Function ǁ Reference, ['collect': Term] )

Purpose	Value
Main focus	track() is a side-effect

Context	Qualifier
Match qualifiers	onmatch
Value qualifiers	onmatch
Name qualifier	optionally expected

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