Text Templates in OCaml

Here’s the OCaml translation of the text templates example:

Our program demonstrates the use of text templates in OCaml. We’ll use the Format module for string formatting and the Printf module for printing.

open Format
open Printf

(* Helper function to create a formatter *)
let create_formatter name format_string =
  let formatter = formatter_of_buffer (Buffer.create 16) in
  let () = fprintf formatter format_string in
  (name, formatter)

(* Main function *)
let () =
  (* Create a simple formatter *)
  let (name, t1) = create_formatter "t1" "Value is %s\n" in
  
  (* Execute the formatter with different values *)
  printf "%s" (asprintf "%a" t1 "some text");
  printf "%s" (asprintf "%a" t1 (string_of_int 5));
  printf "%s" (asprintf "%a" t1 (String.concat ", " ["OCaml"; "Haskell"; "F#"; "Scala"]));

  (* Create a formatter for a record *)
  let (_, t2) = create_formatter "t2" "Name: %s\n" in
  
  (* Execute the formatter with a record *)
  type person = { name : string }
  let jane = { name = "Jane Doe" } in
  printf "%s" (asprintf "%a" t2 jane.name);

  (* Execute the formatter with a map *)
  let mickey = [("Name", "Mickey Mouse")] in
  printf "%s" (asprintf "%a" t2 (List.assoc "Name" mickey));

  (* Conditional formatting *)
  let (_, t3) = create_formatter "t3" "%s\n" in
  let conditional s = if s <> "" then "yes" else "no" in
  printf "%s" (asprintf "%a" t3 (conditional "not empty"));
  printf "%s" (asprintf "%a" t3 (conditional ""));

  (* Iterate over a list *)
  let (_, t4) = create_formatter "t4" "Range: %s\n" in
  let languages = ["OCaml"; "Haskell"; "F#"; "Scala"] in
  printf "%s" (asprintf "%a" t4 (String.concat " " languages))

In this OCaml version:

We use the Format and Printf modules for string formatting and printing.
We create a helper function create_formatter to generate formatters with specific format strings.
The %s format specifier is used instead of {{.}} for value insertion.
We use records and association lists to demonstrate structured data formatting.
Conditional formatting is implemented using a simple function conditional.
List iteration is done using String.concat to join list elements.
The asprintf function is used to apply formatters to values and generate strings.

Note that OCaml’s type system ensures type safety at compile-time, so we don’t need to handle parsing errors as in the original example. The formatting is also more rigid in OCaml, requiring specific types for each format specifier.

To run this program, save it as templates.ml and compile it with:

$ ocamlc -o templates templates.ml
$ ./templates

The output will be similar to the original example, demonstrating various aspects of text formatting in OCaml.

String Formatting in OCaml

Regular Expressions in OCaml

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Title here

Text Templates in OCaml