Re: REGEXP_INSTR range

[Peter Dow <petercdow@xxxxxxxxx>]

Wait, it just occurred to me.  The documentation at

https://www.ibm.com/docs/en/i/7.2?topic=predicates-regexp-like-predicate#rbafzregexp_like__regexp_likecontrol

in "Table 4. Set Expressions (Character Classes)" lists

Example              Description
[A-M]                Range - match any character from A to M. The 
characters to include are determined by Unicode code point ordering.
[\u0000-\U0010ffff]  Range - match all characters.

and from https://chortle.ccsu.edu/FiniteAutomata/Section07/sect07_11.html,

"Rule 3.  Ranges of Characters

To show a range of characters, use square backets and separate the 
starting character from the ending character with a hyphen. For example, 
[0-9] matches any digit. Several ranges can be put inside square 
brackets. For example, [A-CX-Z] matches 'A' or 'B' or 'C' or 'X' or 'Y' 
or 'Z'."

But apparently REGEXP_INSTR is treating [\x00-\x3f] as a list of 3 
bytes, x'00', x'60', and x'3f'.

From what I've read after a lot of googling is that most regex 
implementations deal with strings of characters, not bytes, and 
therefore do not really support ranges of byte values.



On 8/15/2021 5:56 PM, John Yeung wrote:
> On Sun, Aug 15, 2021 at 6:33 PM Peter Dow <petercdow@xxxxxxxxx> wrote:
> > values regexp_instr('abcdef-ghijk' || x'3f', '[\x00-\x3f]') returns 7,
> > which is what I expected.
> >
> > values regexp_instr('- - - - - - - - - - -', '[\x00-\x3F]') returns 1,
> > which is NOT what I expected.
> Why did you expect to find the hyphen in the first example but not in
> the second?
>
> John Y.