[antlr-interest] Control of tab settings in ANTLR 2.7

[shmuel siegel]

In java, the same class (CharScanner), has a method setTabSize(). Lexer 
extends CharScanner so the method is available to the lexer. Sorry, I 
don't use the c++ target so I can't help you any further.

Wigg, J D wrote:
> Hello,
>  
> I am disappointed in not receiving any response to my query (Vol.36, 
> Issue 41, No. 9) about the use and control of tab settings in ANTLR 
> (2.7) which I repeat below.
>  
> Is this because there is a perfectly good description somewhere? If 
> so, I have not been able to find it by searching the ANTLR2 website 
> and I would be grateful if someone could tell me where it is.
>  
> Thank you.
>  
> Question 1.
>
> I want to use a tabsize of 4 characters instead of 8 as assumed in the
> constructors in CharScanner.cpp which I have changed to 4.  Is there
> any other way of altering this value without altering a library
> function?
>
> Question 2.
>
> In order to adjust column numbers correctly I have inserted an action
> after detecting a tab character in the lexer of "tab()" as required
> which should adjust the column number appropriately.
>
> When there is a tab at the beginning of a line, but not elsewhere, the
> column number is incorrect (too many by the tabsize) and the reason
> seems to be that when the tab is at the beginning of a line the tab
> function is entered twice so that the column number is advanced to 9
> instead of only 5 (in my case).
>
> I cannot see any reason for this (there appears to be only one tab at
> the beginning of the line) but I can cure the problem in tab() by first
> checking if the column number is 1 then setting the new column to 2 so
> that on the second entry of tab() the column number is only advanced
> by tabsize once (to 5 in my case) .
>
> Is the function working correctly and, if so, what am I doing wrong?
>
> Thanks,
>
> David.
>
>
>
>
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