Hi Jon, On 22.07.2011 01:09, Jon Graves wrote:

works, while the second doesn't. The second one is the most general one, useful for any situation ... if it worked. Is this a bug?

no, not really. It is documented behaviour, but maybe counterintuitive. In your code ... int n = 2; ex test = power(power(x,n),power(n,-1)); cout << test.subs(power(power(wild(1),wild(2)),power(n,-1))==wild(1)) << endl; cout << test.subs(power(power(wild(1),wild(2)),power(wild(2),-1))==wild(1)) << endl; ... the term power(n,-1) is simplified/evaluated to a numeric 1/2. Therefore the first pattern matches since in its LHS the same simplification takes place. If you want you can look at the data structures with something like cout << tree << test << dflt; The second matching fails because wild(2) is always treated like a symbol and a power with a symbol as a base is not simplified. You try to match a numeric 1/2 with a power(symbol,-1) which doesn't work, because subs() performs purely syntactic substitutions. Regards, Jens