Arevos

What compiler are you using? If I've understood your problem correctly, the usual solution is to increase the look-ahead.

programmingnoob

i am using visual studio.net 2003 ... does it matter in this case?
maybe it does, i am too tired to think of a reason it would though

anyway, how do i increase the look-ahead? As of now, the technique i am using is to start working on the token as soon as the scanner returns one.
In other words, I have not stored the tokens anywhere preserving their order.

do you see what i am saying?

programmingnoob

i hope i made my q clear enough

programmingnoob

I have another q
please take a look at the rule and its abstract syntax tree below:
[HTML]
<stmt-list> ::= <stmt-list> ; <stmt>

;
/ \
/ \
/ \
<stmt-list> <stmt>[/HTML]

The abstract syntax tree is given by my prof.
however, dont you think the abstract syntax tree looks flawed?

let me illustrate with an example...

suppose i have a program that goes like stmt1 ; stmt2

now the tree would be like
[HTML]
;
/ \
/ \
/ \
<stmt2> <stmt1>[/HTML]
but that looks flawed .... doesnt it?
doesnt this make more sense:
[HTML]
;
/ \
/ \
/ \
<stmt1> <stmt2> [/HTML]

but then the above tree doesnt go with the ast given by my prof

what to do

programmingnoob

you can ignore post # 44, i got what i was doing wrong ...

just help me solve the problem discussed in post # 40

The Dark

One way, which you have already mentioned, it to have the ability to put the tokens back into the stream.
Just have a an extra stack in your scanner that holds tokens that have been pushed back. Then when you need to look ahead, push back the tokens afterwards.

programmingnoob

thanks i will look into that

programmingnoob

Consider the rule and its ast below:

[HTML]<stmt-list> ::= <stmt-list> ; <stmt>

;
/ \
/ \
/ \
<stmt-list> <stmt>[/HTML]


suppose i have a lot of stmt's separated by semicolons (meaning they perfectly satisfy the stmt-list rule
also suppose that the tree is supposed to printed like this [node child1 child2]

so shouldnt i expect a lot of semi-colons one after another?

the reason i ask is because i dont see any semi colons next to each other in my printed ast, although there are a lot of stmt's separated by semicolons only
i do see the same number of semicolons, but they are not right next to each other