#pseudocode can be developed from rules of thumb.
     #pseudocode: some problems can be solved by proportions (rule of three), to some order of magnitude
     #pseudocode: enter quantity1,  quantity2, quantity3 and expected output (quantity4) for testcases.
     #pseudocode: enter time in years, number of remaining items
     #pseudocode: output fraction of (remaining items) over (items at time zero)
     #pseudocode: ouput remaining items as fraction or percent
     #pseudocode: output fraction of (quantity4 ) over ( quantity1 at time zero)
     #pseudocode: output fraction of (quantity2) * (quantity3 ) over (quantity1 at time zero)
     #pseudocode: outputs should be in compatible units.
     #pseudocode: rules of thumb can be 3 to 15 percent off, partly since g..in g..out.
     #pseudocode: need test cases > small,medium, giant
     #pseudocode: need testcases within range of expected operation.
     #pseudocode: are there any cases too small or large to be solved?

        # pretty print from autoindent and ased editor
        # Sumerian Seeding Rate Calculator 
        # written on Windows XP on eTCL
        # working under TCL version 8.6.x and eTCL 1.0.1
        # gold on TCL WIKI, 10nov 2014
        package require Tk
        namespace path {::tcl::mathop ::tcl::mathfunc}
        frame .frame -relief flat -bg aquamarine4
        pack .frame -side top -fill y -anchor center
        set names {{} {seed volume silas :} }
        lappend names {field surface area iku :}
        lappend names {seed density kilograms per liter :}
        lappend names {seed volume liters (optional):}
        lappend names {answers: surface area square kilometers  :}
        lappend names {surface area hectares   : }
        lappend names {seed silas per bur: }
        lappend names {seed kilograms per hectare :}
        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 Sumerian Seeding Rate
            from TCL WIKI,
            written on eTCL "
            tk_messageBox -title "About" -message $msg }   
      proc break_flag_routine {     } {
            global side1 side2 side3 side4 side5
            global side6 side7 side8
            global spares 
            global testcase_number
            set t9 $testcase_number
            set product_entries [* $side1 $side2 $side3 $side4 $side5 $side6 $side7 $side8] 
            if { $product_entries < 0.0 } { puts " warning flag! negative numbers detected in product entries ref. tc$t9" }
            foreach item { 1 2 3 4 5 6 7 8 9 10 } {
            set error$item 0 }
            #{-?\d*(\.\d+)?}  regsub -all -- {[^0-9.-]} $input "" number 
            if { $side1 < 0.0 } { set side1 .000001 ; set error1 1  }
            if { $side2 < 0.0 } { set side2 .000001 ; set error1 1  }
            if { $side3 < 0.0 } { set side3 .000001 ; set error1 1  }
            if { $side4 < 0.0 } { set side4 .000001 ; set error1 1  } 
            if { $side5 < 0.0 } { set side5 .000001 ; set error1 1  }
            if { $side6 < 0.0 } { set side6 .000001 ; set error1 1  }
            if { $side7 < 0.0 } { set side7 .000001 ; set error1 1  }
            if { $side8 < 0.0 } { set side8 .000001 ; set error1 1  } 
            if { $error1 == 1 } { puts " warning flag! negative numbers detected, defaulted to positive entries ref. tc$t9" }
            foreach item { 1 2 3 4 5 6 7 8 9 10 } {
            set error$item 0 }
            return 1 }    
       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. ] 
            break_flag_routine
            set barley_density 0.62
            set wheat_density 0.78
            set grain_density $side3
            set side4 $side1
            set side5 [/ [* $side2 3600. 1. ] 1E6 ]
            set side6 [/ [* $side2 3600. 1. ] 1E4 ]          
            set side7 [* [/ $side1 $side2 ] 18.]
            #set side8 [/ [* [* [/ $side1 $side2 ] 18.] $grain_density] 1. ]
            set side8 [/ [* [* [/ $side1 $side2 ] 18.] $grain_density] 6.48 ]
                  }
        proc fillup {aa bb cc dd ee ff gg hh} {
            .frame.entry1 insert 0 "$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
            console show;
            puts "%|table $testcase_number|printed in| tcl wiki format|% "
            puts "&| quantity| value| comment, if any|& "
            puts "&| testcase number:|$testcase_number | |&"           
            puts "&| $side1 :|seed volume silas  |   |&"
            puts "&| $side2 :|field surface area iku  | |& "
            puts "&| $side3 :|seed density kilograms per liter| |& "
            puts "&| $side4 :|seed volume liters |  |&"
            puts "&| $side5 :|answers: surface area square kilometers  |  |&"
            puts "&| $side6 :|surface area hectares   |  |&"
            puts "&| $side7 :|seed silas per bur |  |&"
            puts "&| $side8 :|seed kilograms per hectare   |  |&"
         }
        frame .buttons -bg aquamarine4
        ::ttk::button .calculator -text "Solve" -command { calculate   }
        ::ttk::button .test2 -text "Testcase1" -command {clearx;fillup 240.0 18.0 0.62 240.0 0.0648 6.48 240.0  22.9}
        ::ttk::button .test3 -text "Testcase2" -command {clearx;fillup 270.0 18.0 0.62 270.0 0.0648 6.48 270.0  25.8 }
        ::ttk::button .test4 -text "Testcase3" -command {clearx;fillup 360.0 18.0 0.78 360.0 0.0648 6.48 360.0 43.33 }
        ::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 . "Sumerian Seeding Rate Calculator"