how to make free variable check function in ocaml lambda

Question

I want to make free variable checking function in lambda.

lambda experience is 
type exp =
Var of var
| Lambda of var * exp
| App of exp * exp
and var = string

In checking function, if free variable is included, then return false, else true.

For example, Lambda ("x", Var "x") is true, Lambda ("y", Var "x") is false.

Likely duplicate of https://stackoverflow.com/questions/13783338/free-variables-list-of-a-lambda-expression?rq=1 — Ulugbek Abdullaev, Jun 14 '20 at 13:35
Does this answer your question? [Free variables list of a lambda expression](https://stackoverflow.com/questions/13783338/free-variables-list-of-a-lambda-expression) — Ulugbek Abdullaev, Jun 14 '20 at 13:36

Ulugbek Abdullaev · Answer 1 · 2020-06-14T13:34:45.537

The task seems to be a homework assignment, so it is unlikely to get solution-answers.

A couple of hints:

think of what type should your function have
your function needs to pattern match on exp, so think of how to handle each variant, i.e. Lambda, App, Var.
think of definition of a free variable to help you with handling cases in the hint above

You could also address Benjamin Pierce's book Types and Programming Languages on further reading on this topic.

1 Answers1