Compact dates
DRAFT
Functional style avoids control structures and branches in the program logic.
Sentences that refer to more than two or three dates quickly get confusing. Choices get misunderstood, calls and meetings get missed.
Representing dates tersely helps, provided you can avoid ambiguity. Here is a compact format for a date:
Tu14May2024
Single full date string
Write a lambda cds that returns a string with its date argument in this format; i.e.
q)cds 2024.05.14 / compact date string
"Tu14May2024"
Answer
cds:{[D;M;z] / compact date string
nd:`y`m`d!/:`year`mm`dd$/:(.z.d;z); / now, date
D[z mod 7], #[-2;"0",string nd[1]`d], / day,day#
M[nd[1]`m], / month
string nd[1]`y / year
}[string`Sa`Su`Mo`Tu`We`Th`Fr;
string``Jan`Feb`Mar`Apr`May`Jun`Jul`Aug`Sep`Oct`Nov`Dec; ]
Omit current month or year
Current year and month could be omitted.
Tu14May / omit current year
Tu14 / omit current year and month
cd that returns truncated strings as above.
Answer
cd:{[D;M;z] / compact date string
nd:`y`m`d!/:`year`mm`dd$/:(.z.d;z); / now, date
ym:maxs .[<>]flip nd`y`m; / display year, month?
D[z mod 7], #[-2;"0",string nd[1]`d], / day,day#
M[ym[1]*nd[1]`m], / month
(4*ym 0)#string nd[1]`y / year
}[string`Sa`Su`Mo`Tu`We`Th`Fr;
string``Jan`Feb`Mar`Apr`May`Jun`Jul`Aug`Sep`Oct`Nov`Dec; ]
Refactor
Rewrite cd and cds as projections of a function that takes an extra argument with values:
| value | suppress | example |
|---|---|---|
| 0 | nothing | Tu14May2024 |
| 1 | year | Tu14May |
| 2 | month and year | Tu14 |
| 3 | [year[+month]] according to current date |
any of above |
Answer
FIXME
Date range
A range of two dates could extend the convention.
Tu14May2024-Fr03Jan2025
Tu14May-Fr02Aug
Tu14-Th16May
Write a function cdr that returns a string representing a date range.
q)cdr 2025.05.14 2026.01.03
"We14May2025-Sa03Jan2026"
q)/ assuming in 2024
q)cdr 2024.05.14 2026.01.03
"We14May-Sa03Jan2026"
q)cdr 2024.05.14 2024.08.02
"Tu14May-Fr02Aug"
q)cdr 2024.05.14 2024.05.22
"Tu14-We22May"
Answer
FIXME
Date vector
Write a function cdv that represents a vector of dates.
Assume the dates are in ascending order.
E.g.
q)cdv 2024.05.14+3 16 17 18 59 60 61
"Fr17May Th30 Fr31 Sa01Jun We03 Sa13Jul Su09Mar2025 Mo10 Tu11"
Answer
FIXME
Grouped date vector
Adapt cdv to identify ranges of contiguous dates.
Contiguous dates can be in different months.
q)cdv 2024.05.14+3 16 17 18 59 60 61
"Fr17 Th30May-Sa01Jun We03Jul Sa13Jul Su09-Tu11Mar2025"
Answer
FIXME