Interpreter

Start of Interpreter for program P9.tri at Sun Jun 03 15:10:04 2001
Program
# READ a
y:=((a*3)+(a*2))
WRITE y#
Parsing tree
root
READ
a
:=
y +
*
a 3
*
a 2
WRITE
y
Table of constants
c1=3 c2=2
Table of identifiers
i1=a i2=y

Modified tree
root
READ
a
:=
y +
*
a 3
*
a 2
WRITE
y

Stack id a=0
interpreting the operator READ a
READ
a
:=
y +
*
a 3
*
a 2
WRITE
y
Input a=5

Stack

Stack id y=0

Stack id y=0 id a=5

Stack id y=0 id a=5 const=3
interpreting the operator (a*3)
*
a 3
*
a 2

15 = 5 * 3

Stack id y=0 tm=15

Stack id y=0 tm=15 id a=5

Stack id y=0 tm=15 id a=5 const=2
interpreting the operator (a*2)
*
a 2

10 = 5 * 2

Stack id y=0 tm=15 tm=10
interpreting the operator ((a*3)+(a*2))
+
*
a 3
*
a 2

25 = 15 + 10

Stack id y=0 tm=25
interpreting the operator y:=((a*3)+(a*2))
:=
y +
*
a 3
*
a 2
WRITE
y

y:=25

Stack

Stack id y=25
interpreting the operator WRITE y
WRITE
y
Output y=25

Stack
program P9.tri is completed
THE VARIABLES:
a=5
y=25
Interpreter ended at Sun Jun 03 15:10:09 2001