How scan works and the difference between scan and backslash.

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1

https://learninghub.kx.com/forums/topic/how-scan-works-and-the-difference-between-scan-and

What is the difference between scan and \?

show USTour:([]StartCity:`Boston`NewYork`Washington`Miami`Austin`Chicago;EndCity:`NewYork`Washington`Miami`Austin`Chicago`Boston;wp:0 1 1 1 1 0)
show route:USTour[`StartCity]!USTour[`EndCity]
route scan `NewYork //returns `NewYork`Washington`Miami`Austin`Chicago`Boston

In this situation, I can't seem to use the backslash (I get an error). However, if I want a termination condition (a while loop!) then I need to use the backslash:

(`Austin )route\ `NewYork //returns `NewYork`Washington`Miami`Austin

How can I know which one to use? When is the backslash interchangeable with scan?

2

Hi, 

You can use the keyword scan or the backslash to achieve the same thing here. However the syntax for using the backslash needs to include square brackets []

route scan `NewYork

becomes

route \[`NewYork]

You can read more about Scan here: Accumulators – Reference – kdb+ and q documentation


Hope that helps!

Laura

3

Thank you! And thank you for editing the question. I rewrote it several times (making sure to use plaintext), but the formatting ended up wonky after I pressed post.