Re: Picking Off Lists That Have No Numbers
- To: mathgroup at smc.vnet.net
- Subject: [mg99521] Re: Picking Off Lists That Have No Numbers
- From: yatesd at mac.com
- Date: Thu, 7 May 2009 06:34:45 -0400 (EDT)
- References: <gtrl29$1o5$1@smc.vnet.net>
Here is my understanding of what is going on. In your examples, you are testing for pattern matches with one of the following forms: _Real, _Rational, _String, or _Number. Real, Rational, and String are all valid "Heads". (See help for function Head if you are not familiar with them). Number is not a head. Numbers either have head Real, Rational, Integer, or Complex (as far as I know). The expression Number seems to be only used in relation to importing with the Read function. There is however a FUNCTION NumberQ. So you could create a pattern of the form _?NumberQ (note the important '?' in the expression). Using that instead of _Number should give you the results you expect. _?NumericQ gives similar results, but will treat numbers like pi and e as being numbers too. Hope that helps, Derek Yates