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truncated(?) labels for exponents
http://www.calcudoku.org/forum/viewtopic.php?f=2&t=49
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Author:  jaek  [ Fri Jul 29, 2011 8:56 pm ]
Post subject:  truncated(?) labels for exponents

Today's difficult 8 was a little more difficult that usual for me. The three cell, L-shaped cage that starts in the seventh row is labeled "6^". That looks like 6^1^1 to me, so I entered 1,6,1 early on, but soon ran into a contradiction.

It turns out that 1,6,1 is incorrect and that the label should be "216^". Oddly, both 1,6,1 and the correct triplet passed the puzzle's audits.

A similar thing happened two or three weeks ago as well.

Is anyone else experiencing this? Is anyone seeing the correct "216^" label?

Author:  pnm  [ Fri Jul 29, 2011 9:45 pm ]
Post subject:  Re: truncated(?) labels for exponents

jaek wrote:
It turns out that 1,6,1 is incorrect and that the label should be "216^". Oddly, both 1,6,1 and the correct triplet passed the puzzle's audits.

It's because the exponentiation evaluation is done from right to left.

for 6, 1, 1: 6 ^ (1 ^ 1) = 6 ^ 1 = 6

for 6, 3, 1 (the solution in this case): 6 ^ (1 ^ 3) = 6 ^ 1 = 6

Patrick

Author:  jaek  [ Fri Jul 29, 2011 9:52 pm ]
Post subject:  Re: truncated(?) labels for exponents

pnm wrote:
jaek wrote:
It turns out that 1,6,1 is incorrect and that the label should be "216^". Oddly, both 1,6,1 and the correct triplet passed the puzzle's audits.

It's because the exponentiation evaluation is done from right to left.

for 6, 1, 1: 6 ^ (1 ^ 1) = 6 ^ 1 = 6

for 6, 3, 1 (the solution in this case): 6 ^ (1 ^ 3) = 6 ^ 1 = 6

Patrick


Of course. I was so sure of my incorrect explanation that I couldn't see the fairly obvious correct one. Thanks.

Author:  pnm  [ Fri Jul 29, 2011 10:39 pm ]
Post subject:  Re: truncated(?) labels for exponents

jaek wrote:
Of course. I was so sure of my incorrect explanation that I couldn't see the fairly obvious correct one. Thanks.

I did switch a couple of months ago (was it April?) from left-to-right evaluation
for exponentiation to the more common right-to-left though. So you're not
completely crazy :-)

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