Five easy pieces

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1

Some days it takes me a while to get started. I need to warm up my hands and brain. Hot coffee and a small problem help.

.z.p gives me Co-ordinated Universal Time. A neat way to convert that into a string in the unambiguous ISO 8601 format? That is

q).z.p 2022.03.02D11:50:33.883331000

to give "2022-03-02T11:50:33.883"

 

2

You can use the built in .h.iso8601

q).h.iso8601 .z.p “2022-03-02T12:27:37.506760000” q)-6_.h.iso8601 .z.p “2022-03-02T12:27:37.506”

 

3

Doesn’t get easier than that! 

But the challenge is to code it in q.

4

I would do

@[-6_string .z.p; 4 7 10; :; “–T”]

or if you prefer narrow square brackets then

@[; 4 7 10; :; “–T”] -6_string .z.p

5

I took a similar approach

@[;4 7;:;“-”] string `datetime$.z.p

 

6

Haha. Nice! The good old datetime! I already erased it from my memory

7

Too easy? Too… unnecessary?  Let’s kick it up.

q)ts: .z.d+.z.t q).h.iso8601 ts "2022-03-02T09:12:34.684000000" q).dt.fmtd[;ts] each `iso`dmy`mdy "2022-03-02" "2/3/2022" "3/2/2022"

Write .dt.fmtd without control words: no if, do, while or Cond. 

8

Here is my quick attempt for which I’m sure there is a much more elegant solution 

.dt.fmtd:{(isodmymdy!({ssr[string x;".";"-"]};{"/" sv string ddmmyear$x};{“/” sv string mmddyear$x}))[x] date$y}

 

9

Elegant! But is the datetime type not deprecated?

10

Very well gentlemen, I raze you a substitute for our departed  datetime type with date`time

raze (ssr[;“.”;“-”];“T”,)@'string datetime$.z.p / or alternatively “T” sv (ssr[;“.”;“-”];::)@'string datetime$.z.p

 

 

11

Nice! Though I always wonder about using powerful ssr to replace just one character with another. 

 

q)?[;“-”;] . reverse 1(“.”=)\ string `date$.z.p “2022-03-03”

 

(The Zen monks wanted to play.) 

12

q)f:"T"0:2 1#“dt”$ q)f .z.p “2022-03-04T11:07:52.077” / if you want to be picky about the type q)f:first"T"0:2 1#“dt”$ q)f .z.p “2022-03-04T11:08:49.988”

 

13

Ingenious use of Prepare Text!

Maybe a simpler version of it would be "T"sv string"dt"$.z.p.

14

0: gets you the dashes in the date

15

I would love to know how / why this period to dash conversion is happening if anyone can shed some light?

16

I speculate it’s because it’s the international standard for dates so Prepare Text uses it.

At any rate I should note in the Reference that it does so.

17

Now documented:
https://code.kx.com/q/ref/file-text/#prepare-text