Time Formatting Parsing in Idris

import Data.String
import System.Clock

main : IO ()
main = do
    let p = putStrLn

    -- Here's a basic example of formatting a time
    -- according to ISO8601, which is similar to RFC3339
    t <- systemTime
    p $ show t

    -- Time parsing uses a similar approach to formatting
    let t1 = parseTime "2012-11-01T22:08:41Z"
    p $ show t1

    -- Idris doesn't have built-in time formatting functions like Go,
    -- so we'll demonstrate string manipulation instead
    p $ formatTime (hours 15) (minutes 4)
    p $ formatDate 2006 1 2
    p $ formatDateTime 2006 1 2 15 4 5

    -- For purely numeric representations you can use 
    -- string interpolation with the extracted components 
    -- of the time value
    p $ interpolate "$(show $ year t)-$(padZero $ month t)-$(padZero $ day t)T$(padZero $ hour t):$(padZero $ minute t):$(padZero $ second t)Z"

    -- Parsing will return a Maybe type, which we can pattern match on
    case parseTime "8:41PM" of
        Just time -> p $ show time
        Nothing -> p "Error parsing time"

  where
    formatTime : Int -> Int -> String
    formatTime h m = interpolate "$(show h):$(padZero m)PM"

    formatDate : Int -> Int -> Int -> String
    formatDate y m d = interpolate "$(show y)-$(padZero m)-$(padZero d)"

    formatDateTime : Int -> Int -> Int -> Int -> Int -> Int -> String
    formatDateTime y mo d h m s = 
        interpolate "$(show y)-$(padZero mo)-$(padZero d)T$(padZero h):$(padZero m):$(padZero s)Z"

    padZero : Int -> String
    padZero n = if n < 10 then "0" ++ show n else show n

    parseTime : String -> Maybe Clock
    parseTime = parseISO8601

This Idris code demonstrates time formatting and parsing, although it’s important to note that Idris doesn’t have as robust built-in time handling as Go. We’ve used the System.Clock module for basic time operations and created custom formatting functions to demonstrate similar capabilities.

Here’s a breakdown of the code:

We use systemTime to get the current time, similar to time.Now() in Go.
For parsing, we use a hypothetical parseTime function that would parse an ISO8601 string. Idris doesn’t have this built-in, so you’d need to implement it or use a library.
We create custom formatting functions (formatTime, formatDate, formatDateTime) to demonstrate how you might format times in different ways.
String interpolation is used for formatting, which is similar to Go’s fmt.Printf.
For parsing, we return a Maybe Clock type, which allows us to handle potential parsing errors.

The output of this program would show the current time, a parsed time, and various formatted time strings. The exact format might differ from Go due to differences in how Idris represents time internally.

Remember, Idris is a purely functional language with dependent types, so its approach to time handling is quite different from Go’s. This example aims to demonstrate similar concepts, but the implementation details would vary significantly in a real Idris program.

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Time Formatting Parsing in Idris