regsub problem

[Brian McGinity]

I am working on a regular expression and am having problems with
greedy matching.

Input looks like this:

<for z in (select * from dual) loop>

I would like to turn it into:

<%! zCurrentRow binary_integer; %> <% zCurrentRow:=0; for z in
(select * from dual) loop zCurrentRow:=zCurrentRow+1; %>

Which works with:
regsub -all {<for ([a-zA-z])([a-zA-z0-9_]*) in (.*) loop>} $str {<%!
\1\2CurrentRow binary_integer; %> <% \1\2CurrentRow:=0; for \1\2 in
\3 loop \1\2CurrentRow:=\1\2CurrentRow+1; %>} str

Problem is when more than 1 are present, the greedy match:

<for z in (select * from dual) loop>
<for zz in (select * from dual) loop>

<%! zCurrentRow binary_integer; %> <% zCurrentRow:=0; for z in
(select * from dual) loop>
<for zz in (select * from dual) loop zCurrentRow:=zCurrentRow+1;
%>

How can it know to stop at the first “loop>”?

I’ve tried non-greedy match qualifier: in (.*?) loop ### this
fails

I’ve tried positive lookahead:
regsub -all {<for ([a-zA-z])([a-zA-z0-9_]*) in (((?!loop).)*)} $str
{<%! \1\2currentRow binary_integer; %> <% \1\2currentRow:=0; for \1\2
in \3 loop \1\2currentRow:=\1\2currentRow+1;} str

which is very close:
<%! zcurrentRow binary_integer; %> <% zcurrentRow:=0; for z in
(select * from dual) loop zcurrentRow:=zcurrentRow+1;loop>
<%! zzcurrentRow binary_integer; %> <% zzcurrentRow:=0; for zz
in (select * from dual) loop zzcurrentRow:=zzcurrentRow+1;loop>

The problem is keeps the “loop>” at the end of the result.

Any suggestions with this one?

[Aric Bills]

Try replacing (.*) with ([^>]*).

[Yaroslav Schekin]

> I’ve tried non-greedy match qualifier:   in (.*?) loop

It seems that you need: {<for ([a-zA-z])([a-zA-z0-9_]*?) in (.*?)
loop>}

Also, watch this:

> regexp -about {<for ([a-zA-z])([a-zA-z0-9_]*) in (.*?) loop>}
3 {REG_UNONPOSIX REG_UUNPORT}

> regexp -about {<for ([a-zA-z])([a-zA-z0-9_]*?) in (.*?) loop>}
3 {REG_UNONPOSIX REG_UUNPORT REG_USHORTEST}

So, you didn't actually get shortest match first time. I suggest you
to read re_syntax man page about it.

WBR, Yaroslav Schekin.

[Brian McGinity]

Thank you for helping with this.

> Try replacing (.*) with ([^>]*).

You're suggestion does work in this situation. The only thing when a
where clause is added it can create a problem:

<for z in (select * from dual where 1>2) loop>

A few things crop up which make this hard such as:

<for z in (select * from dual where (1>2 or 2=2) ) loop>

The input could be shorted without the word "loop" if it's easier:
<for z in (select * from dual where (1>2 or 2=2))>

I was thinking a negative lookahead might work...still having issues.

[Aric Bills]

On May 30, 8:17 pm, Brian McGinity <br...@databaseknowledge.com>
wrote:

I don't believe your original post mentioned where clauses, but okay,
here's a regular expression that relies on negative lookahead:

{<for ([a-zA-Z][a-zA-Z0-9_]*) in (((?!loop).)*) loop>}

(NB: This expression consolidates your first two sets of parentheses
into a single one.)

By the way, don't eliminate the word "loop" from the input if you want
to process it with regular expressions.