Concepts of Programming Languages

10.3 Implementing Subprograms with Stack Dynamic Local Variables 453

ARI = activation record instance

n

Functional value

Parameter

Dynamic link

Return (to main)

Local

First ARI

for factorial

ARI

for main

3

?

?

n

Functional value

Parameter

Dynamic link

Return (to factorial)

Second ARI

for factorial

2

?

n

Top

At position 2

in factorial

value

ARI Local

for main^6

Top

In position 3

in main

value

Functional value

Parameter

Dynamic link

Return (to factorial)

Third ARI

for factorial

1

1

third call completed

Functional value Top

Parameter

Dynamic link

Return (to main)

Local

First ARI

for factorial

ARI

for main

(^3) n
6
? value
At position 2
in factorial
first call completed final results
n
Functional value
Parameter
Dynamic link
Return (to main)
Local
First ARI
for factorial
ARI
for main
3
?
?
n
Functional value Top
Parameter
Dynamic link
Return (to factorial)
Second ARI
for factorial
2
2
At position 2
in factorial
value
second call completed
Figure 10.8
Stack contents during execution of main and factorial
of factorial to be multiplied by its parameter value for n, which is 3,
yielding the final functional value of 6, which is then returned to the first
call to factorial in main.