Hello all,

This program compiles, but it gives a wrong output.

program ertext;
{$mode objfpc}{$H+}
uses
Sysutils, regexpr;
var
r: TRegexpr;
i: integer;
BEGIN
r := TRegexpr.create;
try
r.expression := '^(x\s+)*(\([A-E]\))*(\s*.*\.)+(\s+\+.*\b)*()*$';
if r.exec('x (A) Write a report. +ABC +DEF @John @Mary') then
begin
for i := 1 to r.SubexprMatchCount do
begin
writeln(r.match[i]);
readln;
end;
end;
finally
r.free;
end;
END.

The input string is "x (A) Write a report. +ABC +DEF @John @Mary".

The expected output was:

r.match[1] -> " x" -> OK
r.match[2] -> "(A)" -> OK
r.match[3] -> "Write a report." -> OK
r.match[4] -> " +ABC +DEF" -> Error
r.match[5] -> " @John @Mary" -> Error

In stead of 4 e 5, I got only 4 with the following output: " +ABC +DEF @John @Mary".

It's true I am not have enough experience in Regular Expressions, but the used one seems to be very logical for me. Would Someone have any idea what is wrong?

Best regards,

[...] r.expression := '^(x\s+)*(\([A-E]\))*(\s*.*\.)+(\s+\+.*\b)*()*$'; if r.exec('x (A) Write a report. +ABC +DEF @John @Mary') then

The (\s+\+.*\b) matches '+ABC +DEF @John @Mary'.

Mattias

When in doubt, I always recommend "Explain Regex" - there are many such online services. Here is one.

http://rick.measham.id.au/paste/explain.pl?regex=%5Cd%2B(.%5Cd%2B)%3F(%5BeE%5D%5Cd%2B)%3F

Simply paste your regex in the box and click the button. It will then analyse and explain what your regex will do and match.

If still in doubt, I recommend you take a look at RegexMagic [http://www.regexmagic.com/] or RegexBuddy
[http://www.regexbuddy.com/]. These products make it super easy to create working regex statements. Even the 30 day trials will help.

Regards,
- Graeme -

Well, I need to study more. I can't understand what is wrong. The match starts with a blank space: \s+. Some string follows: .*. And it ends in the border of word: \b. So, (\s+.*\b)*, for me, should return: +ABC +DEF. If "@" is not present, why the rest of the string was matched.

My knowledge about Regular Expressions is small, so I really need to study more.

2014-04-10 4:16 GMT-03:00, Mattias Gaertner :

The last ()* can be ignored, because of ()*.
The .* matches anything.
The \b matches any word border, for example the position behind 'Mary'. So the (\s+\+.*\b) matches '+ABC +DEF @John @Mary'.

[...] >> r.expression := '^(x\s+)*(\([A-E]\))*(\s*.*\.)+(\s+\+.*\b)*()*$'; >> if r.exec('x (A) Write a report. +ABC +DEF @John @Mary') then

Mattias