Question

How can I create a partial function application for a non-symmetric operator such as the modulus operator with regards to the first argument without any argument names in F#? My first attempt was

let mod10 = (%) 10 which of course translates to

mod10(x) = 10 mod x instead of the desired

mod10(x) = x mod 10.
Certainly I could write

let mod10 x = (%)x 10 but I’d like to not have to name the argument so is there some placeholder that can be used, something like

let mod10 = (%)_ 10?

Answer 1

You can define flip function which is common in point-free style:

let inline flip f x y = f y x

and use it like this:

let (%-) = flip (%)
let mod10 = (%-) 10

or directly like this:

let mod10 = flip (%) 10

Point-free style is not always readable (as in this example) and not popular in F# programming.