Error in $(x, eval(var)) : invalid subscript type 'language'

[danli349]

Thanks for the excellent book!
Could you please let me know what is wrong with my code?
Thanks.

x <- list(var = 1, y = 2)
var <- "y"
eval(var)
x$var
`$`(x, var)
`$`(x, "var")

x[[var]]
`$`(x, "y")
`$`(x, eval(var))

[1] "y"
[1] 1
[1] 1
[1] 1
[1] 2
[1] 2
Error in `$`(x, eval(var)) : invalid subscript type 'language'