Can anyone explain why the following pattern matches:
[In1]:MatchQ[Hold[a + c + b], Hold[x_ + b + a]]
[Out1]:True
But this one fails:
[In1]:MatchQ[Hold[c + b + a], Hold[x_ + b + a]]
[Out1]:False
It seems that the pattern matcher tries all permutations even if the Plus expression is held (case 1), so why does it fail for case 2?
Many thanks for your help
