Significant digits in a float?

Discussion in 'Python' started by Roy Smith, Apr 28, 2014.

  1. Roy Smith

    Ian Kelly Guest

    It also works if your starting point is (precisely) the north pole. I
    believe that's the canonical answer to the riddle, since there are no
    bears in Antarctica.
    Ian Kelly, May 1, 2014
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  2. Math teacher was selling them in my 10th grade... Actually I already
    owned a Faber-Castell 57/22 "Business" ruler (which did NOT have the CF/DF
    scales set for *PI) and a Pickett N-1010-ES Trig rule.

    I've misplaced the Sterling, but I'm fairly sure it was a deci-trig
    log-log model.

    In the last 15-20 years I've added NIB versions of Faber-Castell 1/54
    Darmstadt, Pickett N-803-ES Dual-Base Log-Log, Pickett Cleveland Institute
    of Electronics N-515-T, and a pair of Sama&Etani/Concise circular pocket
    rules (models 200 and 600).

    Heh... I wonder if the VEs would have noticed the CIE rule had lots of
    electronics formulas on the back, if I'd taken it to the exam session where
    I passed both General and Amateur Extra tests. I couldn't take a calculator
    -- all of mine were programmable. But the slide-rule I took was just about
    as perplexing to the VEs.
    Dennis Lee Bieber, May 1, 2014
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  3. Yeah but that's way too obvious! Anyway, it's rather hard to navigate
    due south from the north pole. Which way do you go? How do you know
    you're still going due south? Will the rocket even light in that

    Important questions must be answered!

    Chris Angelico, May 1, 2014
  4. Roy Smith

    Terry Reedy Guest

    For the most part, there are no bears within a mile of the North Pole
    either. "they are rare north of 88°" (ie, 140 miles from pole).
    They mostly hunt in or near open water, near the coastlines.

    I find it amusing that someone noticed and posted an alternate,
    non-canonical solution. How might a bear be near the south pole? As
    long as we are being creative, suppose some jokester mounts a near
    life-size stuffed black bear, made of cold-tolerant artificial
    materials, near but not at the South Pole. The intent is to give fright
    to naive newcomers. Someone walking in a radius 1/2pi circle about the
    pole might easily see it.
    Terry Reedy, May 1, 2014
  5. Absolutely, snort. I still have my K&E (Keuffel & Esser Co. N.Y.);
    made of wood... (when ships were wood, and men were steel, and sheep ran
    scared) ... to get to the S L T scales I have to pull the slide out
    (turn it over) and reinsert it. You're right, the CF and DF scales are
    missing, but the A B scales have the π symbol where it should be (more
    or less). Mine is the 4058 C model, and you're right... has maths
    equivalents and conversions printed on the back...
    My high school '74 was the last class to learn the slide-rule using
    the Sterling (we paid a deposit to use the school's). I returned my
    Sterling to the teacher at year-end and got my deposit back. They are
    all probably in an old card-board box in the basement. I should ask.
    I received my Pickett Model N4-T Vector-Type Log Log Dual-Base Speed
    Rule as a graduation | birthday gift... off to college with a leather
    cased slip stick hanging from my belt (I was invincable). Mine had the
    CF/m DF/m scales also -- folded at 2.3, the loge of 10 with π where it
    should be (more or less). Copyright 1959... that baby was the king of
    slide rules... I pull it out from time to time, just for warm feelings.
    I carried my slide rule to my general class exam as well. The VE
    inspected it to be sure that certain stuff was not written in pencil
    between the scales! True story. Its not required today, of course, but I
    can still send/receive at 20 wpm. <sigh>

    marcus W0MHH
    Mark H Harris, May 1, 2014
  6. Roy Smith

    Paul Rubin Guest

    There is a nice Javascript simulation of the N4-ES here:

    Some other models are also on that site.
    Paul Rubin, May 1, 2014
  7. Thank you!

    The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES
    on the site is yellow (mine is white) and the site rule indicates Picket
    & Eckel Inc. (that's where the E comes from) Also the the ES states
    Chicage Ill USA where the T states Made in USA.

    The only technical difference is the T scale (which is folded-expanded
    on both). On the ES the T scale is listed only once in the margin. On
    the N4-T the T scale is listed 'twice'!-- once for each part of the
    fold. Well, that gives (2) scales instead of one --for T... increasing
    the number of scales on the rule from 34 to 35... if I'm counting right.
    Which makes the N4-T more valuable... supposedly. I don't plan are
    parting with it... till I croak, then my son (who is studying
    engineering this fall) will inherit it... heh he won't have a clue
    what to do with it !

    The simulated rule on the site above is fabulous... especially if viewed
    from a large wide LED. ... simply fabulouso/ :)

    Mark H Harris, May 1, 2014
  8. The way things are going, the coastline might be
    within a mile of the north pole quite soon.
    Gregory Ewing, May 1, 2014
  9. Well, after having been following the discussion, I couldn't resist
    but post the relevant sketch from the famous Czech play "The Conquest
    of the North Pole by the Czech Karel Němec on 5th April 1909" by Jara
    Cimrman [as "dicovered" and presented by Z. Sverak and L. Smoljak]
    (translated by Craig Cravens) (pp. 38-39)


    Teacher: And now, friends, I’d like to draw your attention to a
    certain geographical
    peculiarity. If I stand next to the chief and step off in any
    direction, I always go south.
    Pharmacist: No!
    Teacher: Yes, yes! Watch! (stands next to the chief and steps off.)
    I’m going south.
    (He returns and sets off in another direction.) And now I’m going
    south again. And now
    —once again south.
    Pharmacist: That’s unbelievable!
    Teacher: Hold on, you haven’t seen anything yet. Richard, stand here
    with your back to
    the chief. And now both of you, step forward.
    (Schwarzenegger and the chief, with their backs to each other, step forward..)
    Did you see that? They’re both going south!
    Pharmacist: That’s really something else!
    Teacher: And I’ve saved the best for last. Now, you’ll really see
    something. Vojtěch,
    mark the Pole with an X and step aside.
    (Vojtěch obeys. The teacher sets off toward the mark.)
    Watch this. I’m going north (he crosses the mark and continues
    walking) and now I’m
    going south! And now back: north … and now south.
    Pharmacist: That’s impossible!
    Teacher: Try it yourself.
    Pharmacist: This I’ve got to see. (He walks towards the pole and
    the<m> moment he
    crosses it his face lights up with joy.) Wow! Friends, this was worth
    it! On the verge of
    death from hypothermia, from hunger, and from exhaustion, but it was worth it!


    Vlastimil Brom, May 1, 2014
  10. Roy Smith

    Roy Smith Guest

    For those who have no idea what we're talking about, take a look at If you just want
    to see what you do with a slide rule, fast forward to 14:20, but you
    really owe it to yourself to invest the 18 minutes to watch the whole
    Roy Smith, May 1, 2014
  11. Roy Smith

    emile Guest

    I was going to bring up London, but as I recall from my brief visit
    there, I wasn't sure you could go one mile straight in any direction.


    emile, May 1, 2014
  12. Roy Smith

    Adam Funk Guest

    It's amazing how big a subthread appeared in response to a gag that I
    think I got from a Car Talk puzzler.

    A recent study conducted by Harvard University found that the average
    American walks about 900 miles a year. Another study by the AMA found
    that Americans drink, on average, 22 gallons of alcohol a year. This
    means, on average, Americans get about 41 miles to the gallon.
    Adam Funk, May 1, 2014
  13. Roy Smith

    Adam Funk Guest

    Adam Funk, May 1, 2014
  14. Roy Smith

    Adam Funk Guest

    OK, change bear to bird & the question to "What kind of bird is it?"
    Adam Funk, May 1, 2014
  15. Roy Smith

    Adam Funk Guest

    I have a "circular" (really spiral) slide rule that I inherited from
    my grandfather.

    One of my uncles told me that he took it (or a similar model) to
    university (ca. 1960, I guess) & got an F on a calculus test because
    his answers were too accurate & precise to be honest. He went to the
    professor's office, showed him the circular slide rule, & got an A.
    Adam Funk, May 1, 2014
  16. A buffalo with an aqualung possibly?
    Mark Lawrence, May 1, 2014
  17. Since calculators had started to appear, I never did get formal
    training in slide-rules. The LL scales still require me to glance at a
    guide book...
    Strangely, out of the three Picketts I now own, only the CIE had the
    belt hook included.
    Interesting -- I've not encountered those scales.
    Whereas I started as a "no-good" Tech. It was the dropping of the code
    requirement that encouraged me to try for the higher ratings. After all,
    using a TS-570 just for 6m is rather limiting <G> [and even that was
    difficult -- for a few months I had a mass PVC piping straddling a fence
    supporting a pair of 6m HamSticks as a dipole... Until the apartment
    manager complained.

    Many moons ago, I could take Gregg shorthand at 100WPM <G> [but my
    typing speed was only a slow 30WPM]

    I regret that I never risked the $35 dollars when my college bookstore
    was closing out the slide-rule display. They had the top Post bamboo
    laminate rule at half price. At the time I'd bought an HP-25 calculator
    [they phased out the HP brand a year or two later -- apparently RPN was too

    And, in a side comment, I once corrected a bookstore that had filed
    Asimov's "Easy Introduction to the Slide Rule" under Science Fiction.
    Dennis Lee Bieber, May 2, 2014
  18. ES was for "Eye-Saver" -- the yellow background vs the bright white of
    the other models.

    For the audience who might be interested...
    (The N515T is available for $95)
    Dennis Lee Bieber, May 2, 2014
    Dennis Lee Bieber, May 2, 2014
  20. Actually, I think you're right. I never used the a yellow rule, but
    I will say that my N4-T never caused me any eye-strain (but I was
    younger then).

    The N4-T was a flat white also... very easy to read. I really don't
    know what all the 'yellow' hype was all about.
    Mark H Harris, May 6, 2014
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