Regex help partial code

Ruby
1

Hello
I have with great effort started on teh regex implemention and am
stuck at one point.
here is my code
(add)\s+\S+\s+[i|s|f]\s+[pei]?\s+

The string is as follows and the tokens are equavalent to
1 token=Add
2 token=any text
3. token=one of the following i or s or f
4.token= 0 or 1 of the following characters [p e i]

I am stuck at the 4th token. i thought ? after the token will give
the 0 or 1 option.
pl correct me if i made a error

seede

2

On Jan 13, 4:25 pm, Junkone [email protected] wrote:

4.token= 0 or 1 of the following characters [p e i]

I am stuck at the 4th token. i thought ? after the token will give
the 0 or 1 option.
pl correct me if i made a error

seede

irb(main):046:0> a=Regexp.new(‘(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s
+’,true)
=> /(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s+/i
irb(main):047:0> a =~(“Add comp i pe”)
=> nil

I dont get match at 4th token

3

On Jan 13, 5:41 pm, Junkone [email protected] wrote:

The string is as follows and the tokens are equavalent to

irb(main):046:0> a=Regexp.new(‘(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s
+’,true)
=> /(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s+/i
irb(main):047:0> a =~(“Add comp i pe”)
=> nil

I dont get match at 4th token

There are a few problems here, I think.
Regexp.new(‘(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s+’,true)

As written, the second token can’t have whitespace. Is that what you
intended?

You want ([isf]) for your third token. That will match a single
instance of one of the three characters.

Also, I’m not clear on what you want for the fourth token. Do you want
0 or 1 of [pei] or 0 or 1 of each of [pei] - which of these are
valid for the fourth token: e or pe.

You should also end the regex with \s* unless there’s always going to
be whitespace. You’re currently checking for one or more whitespace
characters at the end, but your test didn’t have any.

Assuming you do allow 0 or 1 of each of [pei] for the fourth token and
0 or more whitespace characters at the end, I would use:

r = /(add)\s+(\S+)\s+([isf])\s+(p?e?i?)\s*/i

Though, if there can’t be whitespace in any of the tokens, you might
want to use split rather than a regex. The regex above can only get
the fourth token right if the letters are in order - p will match, ei
will match, ip will not. Split wouldn’t have that problem. There may
be a regex way around that, but I can’t think of it at the moment.

“Add comp i ep”.scan r # => [[“Add”, “comp”, “i”, “e”]]
“Add comp i ep”.split # => [“Add”, “comp”, “i”, “ep”]

4

On Mon, 14 Jan 2008, Junkone wrote:

Hello
I have with great effort started on teh regex implemention and am
stuck at one point.
here is my code
(add)\s+\S+\s+[i|s|f]\s+[pei]?\s+

The string is as follows and the tokens are equavalent to
1 token=Add

Unless you use the i modifier, ruby regexps are case sensitive. So
/add/ won’t match /Add/, but /add/i will.

2 token=any text
3. token=one of the following i or s or f

You want /[isf]/ /[i|s|f]/ is probably equivalent to /[isf|]/

4.token= 0 or 1 of the following characters [p e i]
/[pei]?/

I am stuck at the 4th token. i thought ? after the token will give
the 0 or 1 option.
It does.

pl correct me if i made a error

Show the exact regexp and the string it failed on.

John C. Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : [email protected]
New Zealand

5

On Mon, 14 Jan 2008, Junkone wrote:

irb(main):046:0> a=Regexp.new(’(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s
+’,true)
=> /(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s+/i
irb(main):047:0> a =~(“Add comp i pe”)
=> nil

I dont get match at 4th token

irb
irb(main):002:0> /(add)\s+(\S+)\s+([i|s|f])\s+([pei])?\s+/i =~ “Add comp
i pe”
=> nil
irb(main):003:0> /(add)\s+(\S+)\s+([i|s|f])\s+([pei])?/i =~ “Add comp i
pe”
=> 0

The last \s+ insists on matching one or more whitespace chars.

Here is a general recipe for solving this class of problems…

Set up a simple test like I have above…

Delete elements out of the regex until it matches.

The problem was the last one you deleted.

John C. Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : [email protected]
New Zealand