A greeting bot for a colleague from work

Question

I have a colleague at work that works from home every Tuesday and Thursday. At around 8:00 AM he sends us a message with the following text:

Hello today I'm working from home

In order to relieve him from the burden of doing this every day he stays at home, we would like to automate this task for him.

The challenge

Write in as few bytes as possible a piece of code that:

• Receives the current time: your code may receive values for the current year, month (1-12), day of month (1-31), hour (0-23) and minute (0-59) and the day of the week (you can choose whether this number starts from 0 or 1, and if 0/1 means Sunday, Monday or any other day); alternatively you may receive a structure such as Date, DateTime, Calendar or any other time-related structure, if your language allows it. You can also receive a string with the date in yyyyMMddHHmm if you want, or two separate strings for date and time, and then an integer with the day of week. Feel free.
• Returns two consistent truthy and falsey values, indicating if the message must be sent to the work chat or not.

Rules

• This piece of code is assumed to be invoked periodically. The exact periodicity is irrelevant, nonetheless.
• The truthy value must be returned if the day of week is Tuesday or Thursday and the time is 8:00 AM with an error margin of 10 minutes (from 7:50 to 8:10 inclusive).
• The truthy value must be sent only if it is the first time the code is invoked between those hours for the specified day. We don't want the bot to send the same message several times in a row. The way you manage this restriction will be entirely up to you.
• Your code may be an independent program executed repeatedly or it may be part of a bigger code that is always running. Your choice.
• You may assume that there will be no reboots between executions of the code.
• You may assume that the date will always be correct.
• Explanations about your code and specifically about the method used to achieve persistence are encouraged.

Examples

(Week starts on Monday: 1, the following invokations will be made in succession)
2018,08,27,08,00,1 = falsey (not Tuesday or Thursday)
2018,08,28,07,45,2 = falsey (out of hours)
2018,08,28,07,55,2 = truthy (first time invoked this day at the proper hours)
2018,08,28,08,05,2 = falsey (second time invoked this day at the proper hours)
2018,08,28,08,15,2 = falsey (out of hours)
2018,08,29,08,00,3 = falsey (not Tuesday or Thursday)
2018,08,29,18,00,3 = falsey (not Tuesday or Thursday)
2018,08,30,07,49,4 = falsey (out of hours)
2018,08,30,07,50,4 = truthy (first time invoked this day at the proper hours)
2018,08,30,07,50,4 = falsey (second time invoked this day at the proper hours)
2018,08,30,08,10,4 = falsey (third time invoked this day at the proper hours)
2018,08,30,08,11,4 = falsey (out of hours)
2018,09,04,08,10,2 = truthy (first time invoked this day at the proper hours)

This is code-golf, so may the shortest code for each language win!

Answer 1

JavaScript (ES6), 43 bytes

f=(D,t,d)=>5>>d&t>749&t<811&&!f[D]*(f[D]=1)

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Input

• the date as a string in yyyymmdd format
• the time as a string in hhmm format
• the day of week as a 0-indexed integer, with 0 = Tuesday, 1 = Wednesday, ..., 6 = Monday

Output

Returns 0 or 1.

Commented

f = (            // named function, as the underlying object will be used as storage
  D,             // D = date (string)
  t,             // t = time (string)
  d              // d = day of week (integer)
) =>             //
  5              // 5 is 0000101 in binary, where 1's are set for Tuesday and Thursday
  >> d &         // test the relevant bit for the requested day of week
  t > 749 &      // test whether we are in the correct time slot
  t < 811        //
  && !f[D] *     // make sure that this date was not already invoked at a correct time
  (f[D] = 1)     // and store it in the underlying object of f()

Answer 2

Python 3, 69 bytes

f=lambda w,r,*t,l={0}:r not in l!=w in(2,4)<(7,49)<t<(8,11)!=l.add(r)

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Takes input as f(day of the week, date, hours, minutes), where date can be in any consistent format.

Answer 3

APL (Dyalog Unicode), 61 53 50 48 37 36 bytes^SBCS

Anonymous infix lambda. Called with YYYYMMDD f hhmm and then prompts for weekday number; 2 and 4 are Tuesday and Thursday. Redefines the global D to remember dates.

D←⍬
{≢D,←⍺/⍨(⎕∊2 4)∧(⍺∊D)<30≥|780-⍵}

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D←⍬ initialise D to be an empty set

{…} anonymous lambda; ⍺ is YYYYMMDD, ⍵ is hhmm
 780-⍵ difference between 780 (mean of 0750 and 0810) and the time
 | absolute value of that
 30≥ is 30 greater or equal to that?
 (…)< and it is not true that:
  ⍺∊D the date is a member of D
 (…)∧ and it is true that:
  ⎕∊2 4 the prompted for weekday is a member of the set {2,4}
 ⍺/⍨ use that to compress the date (i.e. gives {} if false, {date} if true)
 D,← append that to D
 ≢ and return its tally (i.e. 0 or 1, which are APL's false and true)

Answer 4

Excel formula, 85 bytes

=IF(AND(MID(WEEKDAY(A1)/0,684;3;1)="3";A1-INT(A1)>=0,32638;A1-INT(A1)<=0,34028);TRUE)

Weekday with no parameters are from 1 (Sunday) to 7 (Saturday). The days we want are 3 and 5. Dividing all numbers from 1 to 7 for 0,648, only 3 and 5 gives a result where the first decimal is 3 (Got it by dividing with rand())

Input is inserted on Cell A1

Answer 5

Clean, 343 326 303 279 216 bytes

Clean is so ill-suited to this it's like trying to paint a fence with a chainsaw.

import StdEnv,System.Environment,System._Unsafe
?(y,x,z)=y*480+x*40+z
$y h m d=(d-3)^2==1&&((h-8)*60+m)^2<121&&appUnsafe(setEnvironmentVariable"l"(fromInt(?y)))(maybe 0toInt(accUnsafe(getEnvironmentVariable"l")))< ?y

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Golfing then explaination.

Answer 6

R, 114 106 bytes

function(D,y=D:"%D",u=D$h==7&D$mi>49|D$h==8&D$mi<11&D$w%in%2^4&!y%in%L,`:`=format,`^`=c){L<<-L^y[u];u}
L=F

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Persistence:

Date is checked against L, the list of dates where the code returned TRUE. When the code returns TRUE, today's date is appended to this list. Otherwise the list is not modified.

Saved 6 bytes thanks to @Giuseppe!

Made the code actually work and saved 2 bytes thanks to @digEmAll!

Answer 7

Batch, 109 bytes

@if %3 neq 2 if %3 neq 4 exit/b1
@if %2 geq 07:50 if %2 leq 08:10 if .%1 neq .%l% set l=%1&exit/b0
@exit/b1

Takes input in the form date time dow e.g. 2018-09-04 08:10 2 and outputs via exit code. Explanation: The environment variable l (or any other single letter would work) is used to store the last successful date that passes the test. (The date format itself does not matter as long as it is consistent and does not contain spaces.)

Answer 8

Perl 6, 33 bytes

{811>$^t>749>5+>$^w%2>(%){$^d}++}

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Heavily inspired by Arnauld's solution. Uses the same input format.

Answer 9

C (gcc),  78   50  49 bytes

D;f(d,w,t){w=d-D&&w<4&&w%2&&t>749&&t<811&&(D=d);}

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The expected inputs are:

• d: the date, as a single number yyyymmdd
• w: the day of the week, starting with Monday (0)
• t: the time, as a single number hhmm

Explanation

D;                                      // the date we last said hello.
f(d,                                    // date
    w,                                  // day of the week
      t)                                // time
{
  w=                                    // replaces return
    d-D                                 // if we did not say hello today
       &&w<4&&w%2                       // and we are Tuesday(1) or Thursday(3)
                 &&t>749&&t<811         // and time is between 7:50 and 8:10, inclusive
                               &&(D=d); // then we say hello (evaluated to true) and update D
}

Edits

• Saved 28 bytes thanks to Adám
• Saved 1 more byte, since abs() was actually not helping with the new version

Answer 10

C#, 121 Bytes

int[] d=new int[]{2,4};
double s=>Now.TimeOfDay.TotalSeconds;
bool h=>d.Contains((int)Now.DayOfWeek)&&s>=470&&s<=490;

Moving all three to the same line reduces size to 117 bytes. h is used as a property, just read the value prior to sending the message:

if (h) SendMessage();

Answer 11

F#, 119 bytes

let f w d h m l = if not(l|>Seq.contains d)&&[3;5]|>Seq.contains w&&(h=7&&m>49||h=8&&m<11)then(l@[d],true)else(l,false)

let f w d h m l =

declare function called f with parameters w (day of week) d (date) h (hour) m (minute) l (list of dates it's run on)

if not(l|>Seq.contains d) if the list of dates doesn't contain the passed date

&&[3;5]|>Seq.contains w and the day is Tuesday (3) or Wednesday (5)

&&(h=7&&m>49||h=8&&m<11) and the time is between (exclusive) 7:49 and 8:11

then(l@[d],true) then return a tuple containing the list of dates with the current date appended, and true

else(l,false) else return a tuple containing the list of dates without today and false