Re: RE: Simplify a module

*To*: mathgroup at smc.vnet.net*Subject*: [mg39507] Re: [mg39487] RE: Simplify a module*From*: Dr Bob <drbob at bigfoot.com>*Date*: Thu, 20 Feb 2003 05:13:58 -0500 (EST)*References*: <8EB1C3634596D6118952006008F711CD5BCCDD@debis.com>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

I had left out the definition of 'mytab'. Sorry. Flip's function is apparently a generalized inverse modulo 3, 8 and 49. It satisfies the following tests: test[i_] := And @@ (Mod[#*f@#, i] == If[GCD[#, i] == 1, 1, 0] & /@ Range[1176]) test /@ {3, 8, 49} {True, True, True} Evaluate the following to see where the constants come from (I think): 3*8*49 {1176/#, PowerMod[1176/#, -1, #]} & /@ {3, 8, 49} Times @@@ % Mod[#, {3, 8, 49}] & /@ % The function can also be written as m = If[GCD[#1, #2] == 1, PowerMod[#1, -1, #2], 0] &; f[e_] := Mod[784 m[e, 3] + 441 m[e, 8] + 1128 m[e, 49], 1176] Maybe Flip can clarify what the function is used for. Bobby On Wed, 19 Feb 2003 17:20:54 +0100, Wolf, Hartmut <Hartmut.Wolf@t- systems.com> wrote: > Hey Bobby, > > try to evaluate the appending notebook. It works with me. A problem with > mytab? (I didn't like to spend time on this thread). > > >> -----Original Message----- >> From: Dr Bob [mailto:drbob at bigfoot.com] To: mathgroup at smc.vnet.net >> Sent: Wednesday, February 19, 2003 4:55 PM >> To: Wolf, Hartmut; mathgroup at smc.vnet.net >> Subject: [mg39507] Re: [mg39487] RE: Simplify a module >> >> >> That doesn't work, at least not here on my computer: >> >> sw[{{a_, base_}, seq_}] := (a = Switch[Mod[e, base], >> Evaluate[Sequence @@ seq], _, 0]) >> dcalc4[ein_] := Block[{a1, a2, a3, e = ein}, {T1, M1, T2, M2, T3, M3} = >> {2, 392, 3, 147, 47, 24}; >> Evaluate[sw /@ mytab]; >> Mod[a1*T1*M1 + a2*T2*M2 + a3*T3*M3, 1176]] >> dcalc4[5] >> >> Mod[784 a1 + 441 a2 + 1128 a3, 1176] >> >> For simplicity, I like this one: >> >> m = If[Mod[#, 7] == 0, 0, PowerMod[#, -1, 49]] & /@ Range[0, 48]; >> f[e_] := Mod[784Mod[e, 3] + 441Mod[e, 8]Mod[e, 2] + 1128 m[[1 + Mod[e, >> 49]]], 1176] > > Yes, something to the like, my instinct told me. Yet I didn't like to > delve > into that. And not dwell on this. What I wanted to show was (1) a trick > as > to get at the relevant data from Flips code (2) How to seperate data from > code and (3) that Switch[...] expr. Finis. > > Perhaps you can better see what Flip's doing. These Numbers 784, 1176 ... > are a mystery to me. > >> f[5] >> >> 941 >> >> I was interested in versions of your solution for other reasons. >> >> Bobby >> > > Sure, Bobby, this was meant for Flip! > > Yours, > Hartmut > > -- majort at cox-internet.com Bobby R. Treat