Multiple named tokens in a regexp

Hi all,

I am having a little trouble finding out if you can have named tokens that are optional in a regular expression.

My goal is to seperate a string such as:

'CO(g) [atm] = 1000'

where it has the form

'Parameter [Units] = Value '

However, some Parameter don't have Units

'name = carbon'

If I have a regular expression pattern

'(?<Parameter>[^\[=]+)\s?\[(?<Units>[^\]]+)\]\s?=\s?(?<Value>.*)'

this will only work if all three named tokens are present.

Is there a way of modifying this to make it capture either Parameters,Units,Value or Parameters,Value? I tried to use a none capturing grouping '(?:\[?<Units>[^\]]+)\])?' but that doesn't seem to work right.

Basically, can there be optionally captured Named Tokens? If so, how do you construct the regular expression.

UPDATE:

I used:

(?<parameter>[^\[=]+)\s?\[(?<units>[^\]]+)\]?\s?=\s?(?<value>.*)|(?<parameter>[^\[=]+)\s?=\s?(?<value>.*)

So,

'co [k] = 5'

Parameter = 'co '
Units = 'k'
Value = '5'

And,

'co = 5'

Parameter = 'co '
Units = []
Value = '5'

However, the regular expressions looks very unelegant due to the redundance after the '|'. Anyone have any suggestions how to make it look better?

[Cedric]

The following is a bit simpler, but I wouldn't call it "more elegant" ..

 pattern = '(?<parameter>\S+) \[?(?<unit>[^=\]]*)\]?\s*=\s*(?<value>\w+)' ;