Babylonian Trapezoid Bisection Algorithm and eTCL demo example calculator, numerical analysis

Babylonian Trapezoid Bisection Algorithm and eTCL demo example calculator, numerical analysis

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Preface


gold Here is some eTCL starter code for Babylonian trapezoid bisection algorithm.

Introduction


The Babylonian trapezoid bisection algorithm was loaded into an eTCL calculator. The Babylonians did not use algebra notation, so the reader will have to bear some anachronisms in the eTCL pseudocode. For restating the problem in a computer algorithm, the sides and field area will be in meters and square meters, respectively.


In looking for testcases, some ideal field plans of different scales was constructed from common features of several cuneiform math problems, based on Friberg and DeSegnac. Note that the small triangle comes to a point and can not be treated like a trapezoid with a small side of zero. Some problems appear to use an expansion slice, maybe to be assured of a trapezoid at the smallest section. An iku is 3600 square meters equivalent to 60 meters on side. For the small fields with unit set to 1 meter, the block is equivalent to one iku and 18 blocks are equal to one berum (estate). From the small fields diagram, the larger trapezoid of l/f/h 60/50/60 was loaded into the calculator and returned an area of 3300 square meters with a feed 0.166 and bisection of 55.22 meters. As a check, the area of the small triangle was .5*60*10 or 300 square meters. 300 plus 3300 equals the 3600 square meters of the standard block. From bisection**2 = base**2– feed * Area, bisection**2= 60*60-0.166*3300, bisection = sqrt 3052.2 = 55.246 meters.


For the chart on smallest plots, a sar (garden) is 36 square meters equivalent to 6 meters on the side. With unit set to 1 meter, the block is equivalent to one sar and 100 blocks are equal to one iku (field). The smallest triangle would be (1/2)*b*h = 0.5*6*1 equals 3 square meters. The largest triangle would be (1/2)*b*h = 0.5*6*36 equals 108 square meters.


Pseudocode Section

    # using  pseudocode for Babylonian  trapezoid bisection algorithm. 
    # possible problem instances include trapezoid split in 2 to 7 sections
     long_front = supplied value
     short_front  =  supplied value
     height = supplied value
     solve for bisection length, trapezoid full area, feed (~~ slant info ) 
    # bisection rule  d**2 = (a**2+b**2) /2, d = sqrt ((a**2+b**2) /2)
     set trapezoid_area  h*((a+b)/2)
     set feed ($long_front - $short_front)/$height , negative feed?, need abs
     set bisection  [* [+ [* $long_front $long_front ] [* $short_front $short_front] ] .5 ]
     set bisection [sqrt $bisection ]
     half area =  trapezoid_area  * .5
     quarter area =  trapezoid_area  * .25
     check_answer   trapezoid area =? true_area , second formula   (yes/no)
     set answers and printout with resulting values

Testcases Section


In planning any software, it is advisable to gather a number of testcases to check the results of the program. The math for the testcases can be checked by pasting statements in the TCL console. Aside from the TCL calculator display, when one presses the report button on the calculator, one will have console show access to the capacity functions (subroutines).


Testcase 1

table 1printed in tcl wiki format
quantity value comment, if any
1:testcase_number
20.0 :trapezoid long front meters
10.0 :trapezoid short front meters
14.0 :height meters
0.714 :answers: feed (~ slant info ) meters
52.5 :quarter area square meters
105.0 :half area square meters
210.0 :full area square meters
15.811 :bisection length meters

Testcase 2

table 2printed in tcl wiki format
quantity value comment, if any
2:testcase_number
120.0 :trapezoid long front meters
60.0 :trapezoid short front meters
80.0 :height meters
0.75 :answers: feed (~ slant info ) meters
1800.0 :quarter area square meters
3600.0 :half area square meters
7200.0 :full area square meters
94.868 :bisection length meters

Testcase 3

table 3printed in tcl wiki format
quantity value comment, if any
3:testcase_number
360.0 :trapezoid long front meters
120.0 :trapezoid short front meters
20.0 :height meters
12.0 :answers: feed (~ slant info ) meters
1200.0 :quarter area square meters
2400.0 :half area square meters
4800.0 :full area square meters
268.328 :bisection length meters


Screenshots Section


figure 1.


Babylonian Trapezoid Bisection Algorithm and eTCL demo example screenshot

figure 2.

Babylonian Trapezoid Bisection Algorithm and eTCL demo small scale fields png

figure 3.

Babylonian Trapezoid Bisection Algorithm large scale fields

figure 4.

Babylonian Trapezoid Bisection Algorithm and eTCL demo smallest plots png


References:



Appendix Code


appendix TCL programs and scripts

        # pretty print from autoindent and ased editor
        # Babylonian Trapezoid Bisection Algorithm calculator
        # written on Windows XP on eTCL
        # working under TCL version 8.5.6 and eTCL 1.0.1
        # gold on TCL WIKI, 15jan2017
        package require Tk
        package require math::numtheory
        namespace path {::tcl::mathop ::tcl::mathfunc math::numtheory }
        set tcl_precision 17
        frame .frame -relief flat -bg aquamarine4
        pack .frame -side top -fill y -anchor center
        set names {{} { trapezoid long front meters  :} }
        lappend names { trapezoid short front meters :}
        lappend names { height meters : }
        lappend names { answers: feed (~ slant info )  meters : }
        lappend names { quarter area square meters :}
        lappend names { half area square meters : }
        lappend names { area square meters : }
        lappend names { bisection length meters :} 
        foreach i {1 2 3 4 5 6 7 8} {
            label .frame.label$i -text [lindex $names $i] -anchor e
            entry .frame.entry$i -width 35 -textvariable side$i
            grid .frame.label$i .frame.entry$i -sticky ew -pady 2 -padx 1 }
        proc about {} {
            set msg "Calculator for Babylonian Trapezoid Algorithm   
            from TCL WIKI,
            written on eTCL "
            tk_messageBox -title "About" -message $msg } 
       proc calculate {     } {
            global answer2
            global side1 side2 side3 side4 side5
            global side6 side7 side8 
            global testcase_number 
            incr testcase_number 
            set side1 [* $side1 1. ]
            set side2 [* $side2 1. ]
            set side3 [* $side3 1. ]
            set side4 [* $side4 1. ]
            set side5 [* $side5 1. ]
            set side6 [* $side6 1. ]
            set side7 [* $side7 1. ]
            set side8 [* $side8 1. ] 
            set long_front $side1
            set short_front $side2
            set height $side3
            set feed [abs [/ [- $long_front $short_front ] $height ] ]
            set area [* [* [+ $long_front $short_front] .5 ] $height ]
            # bisection rule  d**2 = (a**2+b**2) /2, d = sqrt ((a**2+b**2) /2)
            set bisection  [* [+ [* $long_front $long_front ] [* $short_front $short_front] ] .5 ]
            set bisection [sqrt $bisection ]
            set side4  $feed
            set side5 [* $area 0.25 ]
            set side6 [* $area 0.5 ]
            set side7 $area 
            set side8 $bisection 
                    }
        proc fillup {aa bb cc dd ee ff gg hh} {
            .frame.entry1 insert 0 "$aa"
            .frame.entry2 insert 0 "$bb"
            .frame.entry3 insert 0 "$cc"
            .frame.entry4 insert 0 "$dd"
            .frame.entry5 insert 0 "$ee"
            .frame.entry6 insert 0 "$ff" 
            .frame.entry7 insert 0 "$gg"
            .frame.entry8 insert 0 "$hh" 
             }
        proc clearx {} {
            foreach i {1 2 3 4 5 6 7 8 } {
                .frame.entry$i delete 0 end } }
        proc reportx {} {
            global side1 side2 side3 side4 side5
            global side6 side7 side8
            global testcase_number reference_factor flag
            console show;
            puts "%|table $testcase_number|printed in| tcl wiki format|% "
            puts "&| quantity| value| comment, if any|& "
            puts "&| $testcase_number:|testcase_number | |& "
            puts "&| $side1 :|trapezoid long front meters |   |&"
            puts "&| $side2 :|trapezoid short front meters| |& "  
            puts "&| $side3 :|height meters| |& "
            puts "&| $side4 :|answers: feed (~ slant info )  meters| |&"
            puts "&| $side5 :|quarter area square meters  | |&"
            puts "&| $side6 :|half area square meters |  |&"
            puts "&| $side7 :|full area square meters  |  |&"
            puts "&| $side8 :|bisection length meters |  |&" 
            }
        frame .buttons -bg aquamarine4
        ::ttk::button .calculator -text "Solve" -command { calculate   }
        ::ttk::button .test2 -text "Testcase1" -command {clearx;fillup 20.0  10.  14.0 .71  52.5  105. 210. 15.8}
        ::ttk::button .test3 -text "Testcase2" -command {clearx;fillup 120. 60. 80. .75  1800.0  3600. 7200. 95. }
        ::ttk::button .test4 -text "Testcase3" -command {clearx;fillup 360.0  120.  20.0 12.66  1200.0  2400.  4800. 268.0 }
        ::ttk::button .clearallx -text clear -command {clearx }
        ::ttk::button .about -text about -command {about}
        ::ttk::button .cons -text report -command { reportx }
        ::ttk::button .exit -text exit -command {exit}
        pack .calculator  -in .buttons -side top -padx 10 -pady 5
        pack  .clearallx .cons .about .exit .test4 .test3 .test2   -side bottom -in .buttons
        grid .frame .buttons -sticky ns -pady {0 10}
               . configure -background aquamarine4 -highlightcolor brown -relief raised -border 30
        wm title . "Babylonian Trapezoid Bisection Algorithm Calculator"      

Pushbutton Operation

For the push buttons, the recommended procedure is push testcase and fill frame, change first three entries etc, push solve, and then push report. Report allows copy and paste from console.

For testcases in a computer session, the eTCL calculator increments a new testcase number internally, eg. TC(1), TC(2) , TC(3) , TC(N). The testcase number is internal to the calculator and will not be printed until the report button is pushed for the current result numbers. The current result numbers will be cleared on the next solve button. The command { calculate; reportx } or { calculate ; reportx; clearx } can be added or changed to report automatically. Another wrinkle would be to print out the current text, delimiters, and numbers in a TCL wiki style table as

  puts " %| testcase $testcase_number | value| units |comment |%"
  puts " &| volume| $volume| cubic meters |based on length $side1 and width $side2   |&"  

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