Contradictory behaviour in pattern matching

Questions
1

Hello,
MatchQ do not seem to treat the inbuilt functions Power and Times in the same way:

In[1]:= MatchQ[Power[a, b], Power[_, _]]

Out[1]= True

In[2]:= MatchQ[Times[a, b], Times[_, _]]

Out[2]= False

An explanation, or what am I doing wrong?
Hans

2

You need HoldPattern to prevent that patter from evaluating to Power[_,2].

MatchQ[Times[a, b], HoldPattern[Times[_, _]]]

Out[19]= True
3

Thanks,
But could you please elaborate on why HoldPattern is needed in case of Times, but not Power?

4

As I stated, Times[_,_] evaluates to Power[_,2]. This happens before MatchQ ever sees its arguments. Power[_,_] on the other hand evalautes to itself. The different matching outcomes are explained by these facts.

5

Yes, as can be seen:

In[4]:= Times[_, _]

Out[4]= _^2

Thanks for very fast response!