Add currentDate as a task in Date.elm

[ThomasWeiser]

We have Date and we have Task, so IMHO we should have a task to get the current date.

This PR implements

Date.currentDate : Task () Date

Of course it could be named differently or could be put into another module. The chosen ones are just my preference.

I didn't write a test within the core library as there are no tests for tasks up to now.
But I did test the code for my own and it works like expected.

[rtfeldman]

seems unlikely that this compiles... 😉

[ThomasWeiser]

Thanks, this should read var currentDate = ..., so I missed the var.
Or do you have other concerns?

[ThomasWeiser]

Here is a simple test app:

import Html
import Date exposing (Date)
import Time
import Task

port execute : Task.Task () ()
port execute =
  Date.current `Task.andThen`
  \date -> Signal.send result.address date

result : Signal.Mailbox Date
result = Signal.mailbox (Date.fromTime 0)

main = Signal.map
  (\date -> Html.text <| toString (Date.toTime date))
  result.signal

[ThomasWeiser]

Here is a simple test app:

import Html
import Date exposing (Date)
import Time
import Task

port execute : Task.Task () ()
port execute =
  Date.current `Task.andThen`
  \date -> Signal.send result.address date

result : Signal.Mailbox Date
result = Signal.mailbox (Date.fromTime 0)

main = Signal.map
  (\date -> Html.text <| toString (Date.toTime date))
  result.signal

[ThomasWeiser]

@dnalot

Why a task?

How would you provide the ability to get the current date? Maybe I am missing something.

Granted, there is already Time.timestamp, which does the same in principal, but

• it's not documented that timestamps actually represent real time/date.
• it's cumbersome to define an extra signal when you need the current date in a task (e.g. send the local time to a server).

IMHO, the core libarary should provide both,

• timestamp as a signal function for needs within the pure Elm-Architecture
• currentDate as a task for needs in the imperative task-based world

[ThomasWeiser]

@dnalot

Why a task?

How would you provide the ability to get the current date? Maybe I am missing something.

Granted, there is already Time.timestamp, which does the same in principal, but

• it's not documented that timestamps actually represent real time/date.
• it's cumbersome to define an extra signal when you need the current date in a task (e.g. send the local time to a server).

IMHO, the core libarary should provide both,

• timestamp as a signal function for needs within the pure Elm-Architecture
• currentDate as a task for needs in the imperative task-based world

[texastoland]

Ha I forgot time isn't referentially transparent. Your implementation looks straightforward! It seems essential for debugging and countdown timers. What's your use case? Feedback: functions generally shouldn't restate their package name. I like JS's Date.now but maybe there are alternatives.

[texastoland]

Ha I forgot time isn't referentially transparent. Your implementation looks straightforward! It seems essential for debugging and countdown timers. What's your use case? Feedback: functions generally shouldn't restate their package name. I like JS's Date.now but maybe there are alternatives.

[ThomasWeiser]

Thanks @dnalot, I renamed the function to Date.current (but Date.now would be equally handy).

[ThomasWeiser]

Thanks @dnalot, I renamed the function to Date.current (but Date.now would be equally handy).

[texastoland]

current is only slightly odd being an adjective. @evancz recommended in #303 vetting new functionality in separate libraries. I didn't see a good fit in existing packages or unpublished repos but it sounds like a superb idea for a new elm-date-extra! @rehno-lindeque might have something to add.

[texastoland]

current is only slightly odd being an adjective. @evancz recommended in #303 vetting new functionality in separate libraries. I didn't see a good fit in existing packages or unpublished repos but it sounds like a superb idea for a new elm-date-extra! @rehno-lindeque might have something to add.

[evancz]

To get this done in a timely manor, I think it makes sense to make a package for time that has nice things in it. We will do a systematic review of these libraries at some point and bring them into core. (plan outlined here)

[evancz]

To get this done in a timely manor, I think it makes sense to make a package for time that has nice things in it. We will do a systematic review of these libraries at some point and bring them into core. (plan outlined here)

[evancz]

Sorry for the long delay on getting you a response @ThomasWeiser. It is hard to juggle all the stuff going on these days!

[evancz]

Sorry for the long delay on getting you a response @ThomasWeiser. It is hard to juggle all the stuff going on these days!

[rehno-lindeque]

An -extra package sounds like a fine idea. @ThomasWeiser we have a bunch of them here https://github.com/circuithub?query=elm- if you're looking for any examples

[rehno-lindeque]

An -extra package sounds like a fine idea. @ThomasWeiser we have a bunch of them here https://github.com/circuithub?query=elm- if you're looking for any examples