[Caml-list] const equivalent for mutable types?

["Christopher A. Gorski" <cgorski@cgorski.org>]

In my code I find that I'm passing a lot of mutable values to functions. 
  Some functions merely read the values.  Others modify the values.  Is 
there a method in OCaml for reproducing behavior similar in spirit to 
the const declaration in C?

Here is a specific case of the general problem:

let t=ref 0
let change r = incr r
let nochange r = Printf.printf "test:%d\n" !r

The problem is that in complex programs I often get confused over what 
functions are modifying values and what functions are not.  I feel like 
I should be able to do something like

let result = change (const r)

and have the compiler give me a type error.

Is there a way to do this in OCaml?  Should I change my programming 
style?  Am I asking a naive question that's already been answered many 
times over in a different form?

-- 
Chris Gorski - http://cgorski.org

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