is it possible to reproduce python's string interpolation in ocaml?

Question

In python, one can use printf like formatting with the "%" operator:

"i am %d years old" % 99

or

"%s is %d years old" % ("bob", 101)

Is there a way to get the same concise syntax in Ocaml, for arbitrary numbers of arguments?

For a single argument, the following works:

let (%) = Printf.sprintf in ... "i am %d years old" % 99

Is there a way that works for arbitrary numbers of arguments?

Answer 1

It depends what you mean by arbitrary numbers of arguments:

• I don't believe there is a way to write a function in OCaml that can accept and unpack a tuple of arbitrary arity (e.g., both (1, "bob") and ("joe", "bob", "briggs")).

• The Caml Way of handling multiple arguments is not through tuples but by currying. If you're willing to do that, then you can just use Printf.sprintf.

• If you really want an infix operator, e.g., something like

  "%s-%s %s is the best movie reviewer" % "joe" "bob" "briggs"
  

  then you're out of luck, because function application binds tighter than any infix operator. You could write

  ("%s-%s %s is the best movie reviewer" % "joe") "bob" "briggs"
  

  but to me that seems kind of beside the point—not the droids you're looking for.

So if your question is:

Can I define, in Objective Caml, an infix version of sprintf that accepts an arbitrary number of arguments?

The answer is no.