How are tail calls and closures in any way Scheme-specific?
The "main value" cited also assumes "pure functional programming" is worthwhile. That is not an uncontroversial opinion, and does little to make the case for SICP to people not already convinced.
The "main value" cited also assumes "pure functional programming" is worthwhile. That is not an uncontroversial opinion, and does little to make the case for SICP to people not already convinced.