Re: Why does this pattern fail to match?

*To*: mathgroup at smc.vnet.net*Subject*: [mg114253] Re: Why does this pattern fail to match?*From*: kj <no.email at please.post>*Date*: Sun, 28 Nov 2010 06:56:46 -0500 (EST)*References*: <iclfej$lb7$1@smc.vnet.net> <ico230$ng8$1@smc.vnet.net>

On Nov 25, 11:57 am, kj <no.em... at please.post> wrote: >> I'm tearing my hair out over this one. Could someone please explain >> to me why all the following MatchQ expressions >> >> MatchQ[Times[ -1, Power[s, -1] ], >> Times[___, Power[___], ___]] >> >> MatchQ[Times[ -1, Power[s, -1]], >> Times[___, Power[___] ]] >> >> MatchQ[Times[ -1, Power[s, -1] ], >> Times[___, _Power , ___]] >> >> return False? (In all cases, s is undefined). And yet, this succeed= >s: >> >> MatchQ[Times[ -1, Power[s, -1]], >> Times[___, _Power ]] >> >> Is there a systematic way to debug/troubleshoot such pattern matching >> problems? Trace is useless here. Thanks for all your replies. Trace is indeed useful here, contrary to what I wrote (it was only the boneheaded way I was using Trace that was useless). ~kj