Re: simple pattern match question

*To*: mathgroup at smc.vnet.net*Subject*: [mg91174] Re: [mg91151] simple pattern match question*From*: Sseziwa Mukasa <mukasa at jeol.com>*Date*: Fri, 8 Aug 2008 07:15:27 -0400 (EDT)*References*: <200808070842.EAA02148@smc.vnet.net>

On Aug 7, 2008, at 4:42 AM, congruentialuminaire at yahoo.com wrote: > Hello UG: > > I am trying to understand simple pattern rule evaulation. The > following trivial examples baffles me: > > --------------------------------------------------- > In[1]:= f[x_Number] := x ^ 2 > In[2]:= f[3] > Out[2]= f[3] > > In[3]:= f[3.3] > Out[3]= f[3.3] > > In[4]:= NumberQ[3.3] > Out[4]= True > -------------------------------------------------- > Why is it that f[3.3] does not evaluate?? for the same reason f[3] does not evaluate, the pattern _Number matches expressions whose head is Number, the head of 3 is Integer the head of 3.3 is Real, neither match. If you want f to only evaluate for real values define it as f[x_Real]. Regards, Ssezi

**References**:**simple pattern match question***From:*congruentialuminaire@yahoo.com