Display Formatted Date and Time using the Standard Library

Task

Date and Time / Display Formatted Date and Time

No packages used

Code

(* The `unix` library, which ships with OCaml's standard library, provides functions to work with dates and times. *) let today: Unix.tm = Unix.localtime (Unix.time ());; (* The `Unix.tm` type represents date and time, but it lacks a pretty printer. We can define one for it. *) let pp_tm ppf t = Format.fprintf ppf "%4d-%02d-%02dT%02d:%02d:%02dZ" (t.Unix.tm_year + 1900) (t.Unix.tm_mon + 1) t.Unix.tm_mday t.Unix.tm_hour t.Unix.tm_min t.Unix.tm_sec;; (* Then define a function that converts `Unix.tm` to string. *) let show_tm = Format.asprintf "%a" pp_tm;; Format.printf "The current date and time is %a" pp_tm today;; print_endline ("The current date and time is " ^ show_tm today);;

let today: Unix.tm = Unix.localtime (Unix.time ());;

let pp_tm ppf t =
  Format.fprintf ppf "%4d-%02d-%02dT%02d:%02d:%02dZ" (t.Unix.tm_year + 1900)
    (t.Unix.tm_mon + 1) t.Unix.tm_mday t.Unix.tm_hour t.Unix.tm_min
    t.Unix.tm_sec;;

let show_tm = Format.asprintf "%a" pp_tm;;

Format.printf "The current date and time is %a" pp_tm today;;

print_endline ("The current date and time is " ^ show_tm today);;

Discussion

• Understanding Unix.tm: The Unix.tm structure represents a local time. This structure includes fields like tm_year, tm_mon, and tm_mday for year, month, and day, respectively.
• Understanding Format: Because Unix.tm is an abstract type, we must define a pretty printer for it. The are usually two kinds of pretty printer for a type: pp uses Format.formatter to print a value, and show simply converts the value to a string.

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