let performOneReduction var term =
    let rec performOneReduction' = function
        | Const(x) -> Const(x)
        | Var(c) when c = var -> term
        | Var(c) -> Var(c)
        | Term(t1, t2) -> Term(performOneReduction' t1, performOneReduction' t2)
    performOneReduction'

let isVar = function
        | Var(c) -> true
        | _ -> false

let variableToChar = function
        | Var(c) -> c
        | _ -> '-'

let termReduction =
    let rec termReduction' = function
        | Const(x) -> Const(x)
        | Var(c) -> Variable(c)
        | Term(t1, t2) -> TermTerm(termReduction' t1, termReduction' t2)
    termReduction'