Postfix

Postfix[f[expr]] prints with f[expr] given in default postfix form: expr//f.

Postfix[f[expr],h] prints as exprh.

Examples

Display a function call in postfix form:

Postfix[f[x]]
(* x // f *)

Use a custom separator:

Postfix[f[x], "@"]
(* x@f *)

Please visit the official Wolfram Language Reference for more details.