Method unifyFunctional

unionfind/unifytypeexpr.go:34–73

(xs []ast.BaseTerm, ys []ast.BaseTerm)

}

func (u *unionFindFun) unifyFunctional(xs []ast.BaseTerm, ys []ast.BaseTerm) error {
	for i, x := range xs {
		y := ys[i]
		xApply, xOk := x.(ast.ApplyFn)
		yApply, yOk := y.(ast.ApplyFn)
		if !xOk && !yOk {
			if x.Equals(ast.Variable{"_"}) || y.Equals(ast.Variable{"_"}) {
				continue
			}
			u.ufrel.parent[x] = x
			u.ufrel.parent[y] = y
			unifyTermsUpdate([]ast.BaseTerm{x}, []ast.BaseTerm{y}, u.ufrel)
			continue
		}
		if yOk && !xOk {
			xApply = yApply
			y = x
			xOk, yOk = true, false
		}
		if xOk && !yOk {
			yVar, yOk := y.(ast.Variable)
			if !yOk {
				return fmt.Errorf("cannot unify %v and %v", x, y)
			}
			if yExisting := u.ufrel.find(yVar); yExisting != nil && !yExisting.Equals(xApply) {
				return fmt.Errorf("cannot unify %v and %v", x, yExisting)
			}

			u.subst[yVar] = xApply
			continue
		}
		if xApply.Function != yApply.Function {
			return fmt.Errorf("cannot unify %v and %v", xApply, yApply)
		}
		if err := u.unifyFunctional(xApply.Args, yApply.Args); err != nil {
			return err
		}
	}
	return nil
}