Re: Matching Or expressions
- To: mathgroup at smc.vnet.net
- Subject: [mg72269] Re: Matching Or expressions
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Sun, 17 Dec 2006 06:20:27 -0500 (EST)
- Organization: The Open University, Milton Keynes, UK
- References: <em0ia6$cbr$1@smc.vnet.net>
Johan Grönqvist wrote: > The context of my problem is explained below. > > I wish to distinguish expressions of the form And[p,q] from those of the > form Or[p,q], but the only thing I find is > MatchQ[myExpr, Or[_]] > and to my surprise I see that MatchQ[And[p,q],Or[_]] is True. Thus I can > not use this to match only the Or-expressions. Above, you are looking for any pattern (the underscore), which will be named "Or". What you want to test is the head of the expression as in the expression below. In[1]:= expr = x == 2 && y == 4; MatchQ[expr, _Or] MatchQ[expr, _And] Out[2]= False Out[3]= True <snip> Regards, Jean-Marc