Bourbaki dangerous bend symbol: Difference between revisions
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[[File:Borne_Michelin_Virages.JPG|thumb|left|French "virages dangereux" road sign, before 1949.]] |
[[File:Borne_Michelin_Virages.JPG|thumb|left|French "virages dangereux" road sign, before 1949.]] |
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The '''dangerous bend''' or '''caution''' symbol ☡ ( |
The '''dangerous bend''' or '''caution''' symbol '''☡''' ({{unichar|2621|CAUTION SIGN}}) was created by the [[Nicolas Bourbaki]] group of mathematicians and appears in the margins of [[mathematics]] books written by the group. It resembles a [[Traffic sign|road sign]] that indicates a "dangerous bend" in the road ahead, and is used to mark passages tricky on a first reading or with an especially difficult argument.<ref>Steven G. Krantz (2011), ''[http://books.google.com/books?id=mMZBtxVZiQoC&pg=PA92 The Proof Is in the Pudding: The Changing Nature of Mathematical Proof]'', Springer, ISBN 0-387-48908-8, p. 92.</ref> |
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Others have used variations of the symbol in their textbooks, and computer scientist [[Donald Knuth]] introduced a more realistic road-sign depiction in his [[Metafont]] and [[TeX]] systems, with a pair of adjacent signs indicating doubly dangerous passages.<ref>Donald Ervin Knuth (1984), ''[http://books.google.com/books?id=hEYuAQAAIAAJ The TeXbook]'', Addison-Wesley, ISBN 0-201-13448-9.</ref><ref>Donald Ervin Knuth (1986), ''[http://books.google.com/books?id=GghUAAAAMAAJ The METAFONTbook]'', Addison-Wesley, ISBN 0-201-13445-4.</ref><ref>George J. Tourlakis (2003), ''[http://books.google.com/books?id=nparMXao59QC&pg=PR14 Lectures in Logic and Set Theory, Volume 2: Set Theory]'', Cambridge University Press, ISBN 0-521-75374-0, p. xiv.</ref> |
Others have used variations of the symbol in their textbooks, and computer scientist [[Donald Knuth]] introduced a more realistic road-sign depiction in his [[Metafont]] and [[TeX]] systems, with a pair of adjacent signs indicating doubly dangerous passages.<ref>Donald Ervin Knuth (1984), ''[http://books.google.com/books?id=hEYuAQAAIAAJ The TeXbook]'', Addison-Wesley, ISBN 0-201-13448-9.</ref><ref>Donald Ervin Knuth (1986), ''[http://books.google.com/books?id=GghUAAAAMAAJ The METAFONTbook]'', Addison-Wesley, ISBN 0-201-13445-4.</ref><ref>George J. Tourlakis (2003), ''[http://books.google.com/books?id=nparMXao59QC&pg=PR14 Lectures in Logic and Set Theory, Volume 2: Set Theory]'', Cambridge University Press, ISBN 0-521-75374-0, p. xiv.</ref> |
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==Typography== |
==Typography== |
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[[File:Knuth's dangerous bend symbol.svg|thumb|60px|right|Knuth's "Dangerous Bend" sign]] |
[[File:Knuth's dangerous bend symbol.svg|thumb|60px|right|Knuth's "Dangerous Bend" sign]] |
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Revision as of 19:57, 9 May 2012
Certains passages sont destinés à prémunir le lecteur contre des erreurs graves, où il risquerait de tomber; ces passages sont signalés en marge par le signe ☡ («tournant dangereux»)
Some passages are designed to forewarn the reader against serious errors, where he risks falling; these passages are signposted in the margin with the sign ☡ ("dangerous bend")
— Nicholas Bourbaki's description of the symbol in several textbooks[1]
The dangerous bend or caution symbol ☡ (U+2621 ☡ CAUTION SIGN) was created by the Nicolas Bourbaki group of mathematicians and appears in the margins of mathematics books written by the group. It resembles a road sign that indicates a "dangerous bend" in the road ahead, and is used to mark passages tricky on a first reading or with an especially difficult argument.[2]
Others have used variations of the symbol in their textbooks, and computer scientist Donald Knuth introduced a more realistic road-sign depiction in his Metafont and TeX systems, with a pair of adjacent signs indicating doubly dangerous passages.[3][4][5]
Typography
In HTML the unicode dangerous bend symbol ☡ can be produced by:
- ☡
In the LaTeX typesetting system, Knuth's dangerous bend symbol can be produced by first loading the font manfnt (a font with extra symbols used in Knuth's TeX manual) with
- \usepackage{manfnt}
and then typing
- \dbend
There are several variations given by \lhdbend, \reversedvideodbend, \textdbend, \textlhdbend, and \textreversedvideodbend.
References
- ^ See, for example, Théorie des ensembles, p. I-8.
- ^ Steven G. Krantz (2011), The Proof Is in the Pudding: The Changing Nature of Mathematical Proof, Springer, ISBN 0-387-48908-8, p. 92.
- ^ Donald Ervin Knuth (1984), The TeXbook, Addison-Wesley, ISBN 0-201-13448-9.
- ^ Donald Ervin Knuth (1986), The METAFONTbook, Addison-Wesley, ISBN 0-201-13445-4.
- ^ George J. Tourlakis (2003), Lectures in Logic and Set Theory, Volume 2: Set Theory, Cambridge University Press, ISBN 0-521-75374-0, p. xiv.