ASTTArrow.java

import java.util.Set;

public class ASTTArrow implements ASTType {
    ASTType dom;
    ASTType codom;

    public ASTTArrow(ASTType d, ASTType co) {
        dom = d;
        codom = co;
    }

    public ASTType getCodom() {
        return codom;
    }

    public ASTType getDom() {
        return dom;
    }

    @Override
    public String toStr() {
        return "("+dom.toStr()+"->"+codom.toStr()+")";
    }   

    @Override
    public boolean eqt(ASTType t)
    {
        if (t instanceof ASTTArrow) {
            ASTTArrow ta = (ASTTArrow)t;
            return (codom.eqt(ta.getCodom()) && ta.getDom().eqt(dom));
        }
        return false;   
    }

    @Override
    public boolean subtypeOf(ASTType t, Environment<ASTType> e, Set<String> seen) throws InterpreterError {
        t = ASTTypeDef.unfold(t, e);
        if (!(t instanceof ASTTArrow other))
            return false;

        boolean argsMatch = other.getDom().subtypeOf(this.dom, e, seen);
        boolean returnMatch = this.codom.subtypeOf(other.getCodom(), e, seen);
        return argsMatch && returnMatch;
    }
}