pub mod util;
pub mod display;
pub mod check;


use crate::sexp::SExp;


#[derive(Clone,Debug,PartialEq)]
pub enum Type {

    Integer,

    Arrow(Box<Type>, Box<Type>),

    List(Vec<Type>),

    UndefinedType, // only for errors

}


#[derive(Debug,PartialEq)]
pub enum TypeError {

    UndefinedVariable(String),

    InvalidOperator {
	operator: SExp,
	expected: Type,
	found:    Type,
    },

    InvalidArgList {
	arglist:  SExp,
	expected: Type,
	found:    Type,
    },

    OtherError
}