Turtle graphics: hidden features in APL2

ABSTRACT

Twenty-five years ago Martin Gardner wrote an article in "Mathematical Games" of the Scientific American with the title Fantastic patterns traced by programmed "Worms" [Gar 1]. Later on these worms were called "turtles". These turtle graphics are well known from the LOGO-system [Ab/diS].These graphics are also vector graphics not made by setting absolute coordinates but by setting relative increments of distances and angles. With tiny APL2 idioms I have developed many 2D-graphics. It has happened in a short time in a normal manner and as a dialogue form. My top is "one-liner as eye liner"

REFERENCES

• AB/DIS: ABALSON, HAROLD aad DI SESSA, ANDREA: Turtle Geometry, MIT Press, 1980
• BEN: BENN, DAVID ~.: Turtle Graphics andf VECTOR Vol. 12, No. 3, Jan 1996, p. 79- 97
• CLA: James Clayson, Visual modeling with Logo, MIT Press, Cambridge, MA, 1988
• CRI: CRITCHLOW, KEITH: Islamic Patterns, Thames and Hudson, 1976, reprinted 1995
• DEW: DEWDNEY, A, K.: Imagination meets geometry in the crystalline realm of latticework On Computer Recreations), Scientific American, June 1988, p. 100 - 103
• GAR 1: GARDNER, MARTIN: Fantastic patterns traced by programmed "worms" On Mathematical Games), Scientific American, November 1973, p.116-123
• GAR 2: GARDNER, MARTIN: On tessellating the plane with convex polygon tiles ~n Mathematical Games), Scientific American, July 1975, p.112 -117, further articles Aug 1975 and Jan 1977
• GR/SH 1: Branko Grünbaum , G C Shephard, Tilings and patterns, W. H. Freeman & Co., New York, NY, 1986
• GR/SH2: GRON13AUM, BRANKO and G. C: SHEt'HARD: Tiling by Regular Polygons, Mathematics Magazines, Vol. 50, No. 5, November 1977, p. 227 - 247
• HAY: HAX'ZS, BRIAN: Turning turtle gives one a view of geometry from the inside out, (in Computer Recreations), Scientific American, February 1984, p. 12- 16
• JON: ~ONES, OWEN: Grammar of Ornaments, (1856), reprint Parkland, 1995
• KAP: Jay Kappraff, Connections: the geometric bridge between art and science, McGraw-Hill, Inc., New York, NY, 1991
• RA/BA: RAMA, HENDRm and BARGHOORN, MARTIN: TURTLEGRAPHICS WtTH APL2, VECTOR, Vol. 13, No. 4, April 1997
• WELD: WELLS, DAVID: The Penguin Dictionary of Curious and Interesting Geometry, Penguin Books, 1991
• WI: W ICHMANN, BRIAN: An encyclopaedia of tiling patterns, the mathematical gazette, November 1994, Vol. 78, No. 483, p. 265 - 275

INDEX TERMS

Primary Classification:
  F. Theory of Computation
  F.3 LOGICS AND MEANINGS OF PROGRAMS

General Terms:
Design, Languages