Re: Do-loop conversion

• To: mathgroup at smc.vnet.net
• Subject: [mg50283] Re: [mg50211] Do-loop conversion
• From: "David Annetts" <davidannetts at ihug.com.au>
• Date: Tue, 24 Aug 2004 06:22:30 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```Hi Rich,

<snippage>

Do[
wavevectmap := wavetabc[revdelta, revbeta, phi];
leftvectmap := leftvectmapc[wavevectmap];
thtest := thtestcomp[revrough, leftvectmap, wavevectmap];
maproughrev := roughrevcomp[thtest];
coeffmap := coeffcomp[wavevectmap, leftvectmap, maproughrev];
phasemap := phasecomp[wavevectmap, revthick];
coeffs := fcoeffcomp[coeffmap, phasemap];
recurr[prior_, {fc_, pf_}] := (fc + (prior*pf^2))/(1 +
(fc*prior*pf^2));
intensity := intensitycomp[Fold[recurr, 0, coeffs ]];
newdata = newdatacomp[phi, intensity, params];
newc = AppendTo[newc, newdata],
{phi, phistart, phiend, phiinc}]

<snippage>

-------------------

An easy(!) way into a functional style might be ...

1. define phirange = Range[phistart, phiend, phiinc];
2. map this range using

newc = (
wavevectmap := wavetabc[revdelta, revbeta, #];
leftvectmap := leftvectmapc[wavevectmap];
thtest := thtestcomp[revrough, leftvectmap, wavevectmap];
maproughrev := roughrevcomp[thtest];
coeffmap := coeffcomp[wavevectmap, leftvectmap, maproughrev];
phasemap := phasecomp[wavevectmap, revthick];
coeffs := fcoeffcomp[coeffmap, phasemap];
recurr[prior_, {fc_, pf_}] := (fc + (prior*pf^2))/(1 +
(fc*prior*pf^2));
intensity := intensitycomp[Fold[recurr, 0, coeffs ]];
newdata = newdatacomp[#, intensity, params];
)& /@ phirange

Another speed improvement might be to precompute wavevectmap and using it as
a table lookup; from your code excerpt, there's no need to have this inside
the loop.

Regards,

Dave.

```

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