 Display for lexical scope

A table of pointers supporting direct access to active lexical environments without traversing a static chain. A conventional display is indexed by lexical level; a procedure-indexed alternative keeps the newest activation of each procedure and saves and restores the previous table entry on entry and return.

For direct calls under lexical scope, the executing activation's static chain contains the newest surviving activations of its enclosing procedures. This follows by mathematical induction on calls and returns: a direct call inherits a suffix of the caller's chain, and a return restores the previous chain after intervening activations finish. With procedural parameters, a passed programming closure can instead refer to an older still-active enclosing activation, so simply consulting the newest-activation table is insufficient.