CAR (current activation record)

7.5:

. a var`init associates a var`instantiation

with a particular subroutine or block activation

(stacked activation record, or act'rec)

. at the end of the act'rec (when the stack gets rolled back),

a type-class gets another call to close

-- this doesn't need a parameter because it implicitly refers to

the current act'rec .

this is done without the programmer,

by translating var creations into these {init, close} pairs of calls .

7.6:

. when a subprogram starts up,

it needs space for its own locals,

and when done, then it needs to release its own locals .

. this space typically comes from a combination of

the system's stack and heap .

. the elaboration of a declare block or subprogram call

results in the creation of a new scope,

meaning it creates a new activation record on the stack,

referred to as the [current activation record] (CAR) .

. for the sake of modularity,

the computer's heap space should be decomposed into

separate subheaps for each subprogram call .

. this will make it easy to both get the memory back

after the subprogram returns,

and associate each object with a particular subheap .

. so then, in its simplest incarnation,

the CAR on the stack is simply a pointer to a subheap;

and, when the subprogram returns,

it can simply dispose of its one subheap

rather than asking each involved type-mgt

to recycle its own objects .

. when a scope creates a new variable of type"T,

it's calling T`type-mgt to implicitely use CAR space

to allocate a piece of the subheap and initialize it .