*To*: Lars Noschinski <noschinl at in.tum.de>*Subject*: Re: [isabelle] a simplifier question 2*From*: noam neer <noamneer at gmail.com>*Date*: Mon, 8 Jun 2015 12:20:02 +0300*Cc*: "cl-isabelle-users at lists.cam.ac.uk" <cl-isabelle-users at lists.cam.ac.uk>*In-reply-to*: <5573EED3.8000108@in.tum.de>*References*: <CAGOKs09o8XAiVVm=GdjMAz3ezFQM93uiQVJ_Ugv3Z6Pg9sDxZQ@mail.gmail.com> <5573EED3.8000108@in.tum.de>

thanx for the explanation. however, note that in the third proof I didn't write > apply (simp add: power_add) but > by (simp add:power_add [of a 3 3]) so I'm adding "a^(3+3)=a^3 * a^3" to the simp set. this doesn't match directly, but why wasn't the simplifier able to simplify it to "a^6 = a^3 * a^3" ? On Sun, Jun 7, 2015 at 10:12 AM, Lars Noschinski <noschinl at in.tum.de> wrote: > On 07.06.2015 01:30, noam neer wrote: > > [simplifier questions] > > The simplifier performs (primarily) rewriting. A term t will be > rewritten with an equation s = s' if there is some substitution of the > variables Ï, such that t is syntactically equal to sÏ. Then t is > replaced by s'Ï. The simplifier tries to do this for all subterms of the > goal. > > Recall, power_add is the theorem: ?a ^ (?m + ?n) = ?a ^ ?m * ?a ^ ?n > > Now, for your proof attempts: > > > lemma > > fixes a::real > > shows "a^6 = a^3 * a^3" > > using [[simp_trace=true]] > > using power_add [of a 3 3] > > by simp > > This works as the simplifier can rewrite "3 + 3" to 6 and can then solve > the goal by rewriting with "a^6 = a^3 * a^3". > > > using power_add > > The simplifier cannot rewrite "?m + ?n" to anything. It also does not > match the "6" in the goal. > > > apply (simp add: power_add) > > Similar. "a^6" does not match "?a ^ (?m + ?n)". > > In my opinion, the nicest proof is: > > apply (simp add: power_add[symmetric]) > > The [symmetric] reverses the equation. > > -- Lars > > > -- I can't see very far, I must be standing on the shoulders of midgets.

**Follow-Ups**:**Re: [isabelle] a simplifier question 2***From:*Manuel Eberl

**References**:**[isabelle] a simplifier question 2***From:*noam neer

**Re: [isabelle] a simplifier question 2***From:*Lars Noschinski

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