Thanks for the replies on how to begin to think about a Context. vs Environments.

Next up in the SICP study are the terms. applicative order evaluation where the operands are evaluated first and  normal order evaluation, the operands are not evaluated until their values are needed.

I vaguely remember Eliot relying on Squeak strict Right to Left (or is it Left to Right) evaluation rule in an email from some years ago.

Thank you in advance.

t