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Date: Tue, 15 Mar 2011 19:54:53 +0100
From: Alain Frisch <alain@frisch.fr>
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Subject: [Caml-list] How to let the user choose a format string?

Hi all,

I'd like to write a function

val fmt: string -> float -> string

which takes a string, parses it as a format string of type expecting a 
single float argument, and applies this format string to a given float. 
Expected behavior:

# fmt "%+.2f" 32.;;
- : string = "+32.00"
# fmt "%+.2i";;
--> some exception


I've come up with:

let fmt s = Scanf.sscanf (Printf.sprintf "%S" s) "%{%f%}" Printf.sprintf

which seems to work. Is this indeed supposed to work? Is there a better 
way to achieve the same behavior without having to parse the format 
string by hand?



Alain