discovered that emacs has a bundled library for functional programing pattern matching! The package file is 〔pcase.el〕. It's part of GNU Emacs 24.3.1.
it's written by Stefan Monnier, a professor of functional programing research, and one of the two current leader of emacs dev.
you can get to the file by calling
pcase-let, then click on the file name.
Note: ML stands for Meta Language. It was a family of languages. Current popular decendents include OCaml and Microsoft's FSharp. 〔☛ Xah's OCaml Tutorial〕 Among functional programing languages, OCaml is one of those that's heavily used in the industry (⁖ Mldonkey, Unison 〔☛ Unison Tutorial〕), especially in math formal proof systems ⁖ Coq. And it's famously used in JaneStreet. 〔☛ OCaml Use in Industry: Janestreet Talk by Yaron Minsky 📺〕
Proof systems written in OCaml includes: Coq, HOL Light. 〔☛ State of Theorem Proving Systems 2008〕
Also, the designer of ML is Robin Milner (1934 〜 2010), he died in recent years.