Mailing List Archive: Extract substring using offsets?

[REBOL] Extract substring using offsets?

From: kevin_kelleher:non:hp at: 16-Mar-2001 9:06


Is there a way in Rebol to extract a substring using offsets?
For example, if I have a string 100 characters long, and
I want to get characters 25-50, what can I do?

If there is a simple positive answer to that question,
you can stop here.  If not, read the following:

To put this question in context, what I'm trying to do is
extract a table block out of an html page.   What I do is
this:
----------------------------------------------------------------------------
-----------
; --- read the page into a variable

ad: read %index.html

; --- get the offsets on the open-table tags

htmlTables: make block! 40
parse ad [any [to "<table" mark: thru ">"
	(append htmlTables index? mark
	 append htmlTables "+")]
]

; --- get the offsets for the close-table tags

parse ad [any [to "</table" mark: thru ">"
	(append htmlTables index? mark
     append htmlTables "-")]
]

; --- order them by offset

sort/skip htmlTables 2

; --- get the seventh open-table tag (it just happens to be the one I want)

openTagCount: 0
while [openTagCount < 7] [
    openTable: copy/part htmlTables 2
	remove/part htmlTables 2
	if openTable/2 = "+" [ openTagCount: openTagCount + 1 ]
]

; --- get the corresponding close tag (remember that tags can be nested)

openTagCount: 1
while [openTagCount > 0] [
	closeTable: copy/part htmlTables 2
	remove/part htmlTables 2
	either closeTable/2 = "+"
		[ openTagCount: openTagCount + 1 ]
		[ openTagCount: openTagCount - 1 ]
]

----------------------------------------------------------------------------
------------------

Okay, so now I have the offsets; can I do anything with them?
Do I need to take a different approach?

Kevin Kelleher