Construct with user types safely with capital letter

Learning
,
1 
module Probability : sig
    type probability = private Pr of float
    val create : float -> probability
end = struct
    type probability = Pr of float
    let create x = assert (1.0 >= x && x >= 0.0); Pr x
end

pr = Probability.create is not nice, as I construct a tree by let cT = Leaf 0.3 with capital L for example. For consistency I want let p = Pr 0.3.

I don’t know if that is even possible. Private types page wasn’t helpful. Am I following the wrong coding practices?

2

The best thing I could think of is

module Pr = struct
    include Probability
    let c = Probability.create
end

Then we can use Pr.c. Any better alternatives?

3

One approach is to use an underscore prefix for the name of “smart constructor” functions. So e.g. in the OP you could rename create to _Pr.

4

I personally don’t like to prefix values with an underscore because the compiler treats those specially, and they don’t trigger warnings when unused. Another option that some libraries use is v (for “value”) instead of c as their main constructor function.

The short answer to your question is no, you can’t name a value beginning with a capital letter. If you simply want everything that constructs a value to look the same, then your best option is in the other direction: add functions for your other variant constructors and use those. Then all of your constructors will be consistently lowercase.

(However, I think it’s easier to just embrace the fact that different OCaml values are constructed with different syntaxes instead of trying to make them all the same.)

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