Java Reference
In-Depth Information
procedure
S
tart
()
switch
(
)
case
ts
.
peek()∈{num, lparen}
ans
←
...
V
alue
()
call
match
( $ )
call
print
(
ans
)
5
end
function
V
alue
()
returns
int
switch
(
)
case
ts
.
peek()∈{num}
call
...
match
( num)
num
.
ValueOf()
return
(
ans
)
case
ts
.
peek()∈{lparen}
call
ans
←
match
( lparen)
ans
←
E
xpr
()
call
( rparen)
return
(
ans
)
match
end
function
E
xpr
()
returns
int
switch
(
)
case
ts
.
peek()∈{plus}
call
...
match
( plus)
op
1
←
V
alue
()
6
op
2
←
V
alue
()
7
+
op
2
case
ts
.
peek()∈{prod}
call
return
op
1
8
match
( prod)
ans
←
V
alues
(1)
9
return
(
ans
)
end
function
V
(
thus f ar
)
returns
int
case
ts
.
peek()∈{num, lparen}
alues
next
←
V
alue
()
10
ans
←
V
alues
(
thus f ar
×
next
)
11
return
(
ans
)
case
ts
.
peek()∈{rparen}
return
thus f ar
12
end
Figure 7.10: Recursive-descent parser with semantic actions. The
variable
ts
is the token stream produced by the scanner.
